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CSIKO DEVELOPS NEW M ULTI-SATELLITE ANTENNA FOR PAY TV

Top Selling Electronics Magazine

Registered by Australia Post - Publiication No. NBP 0240

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OCTOBER 1992

Aust* $4.95

NZ $6.95 incl GST

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AUSTRALIAN

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Test and Measurement

READER INFO NO. 1

Volume 54, No. 10

October 1992

AUSTRALIA’S LARGEST SELLING ELECTRONICS MAGAZINE — ESTABLISHED IN 1922

Video and Audio

6 WHAT’S NEW IN VIDEO & AUDIO The latest products...

8 I CAN SEE CLEARLY NOW New Australian CRT anti-glare process
12 THE CHALLIS REPORT: Philips new DCC-900 digital tape recorder

Features

20 VENUS MAPPING DONE, MAGELLAN NEARS END NASA’s probe
28 WHEN I THINK BACK... Fred Thom and the Tasma story — 2
44 AOTC’S NEW CELLULAR MOBILE NETWORK - 2 GSM’s advantages
48 MOFFAT’S MADHOUSE A musical battle of the sexes

Projects and Technical

34 HIGH QUALITY STEREO AMP USING VALVES - 2 Building & testing
50 THE SERVICEMAN ‘Not worth fixing items rescued from the tip...

60 BASIC ELECTRONICS - 16 The operational amplifier
66 FLEXIBLE LOUDSPEAKER PROTECTION CIRCUIT Low cost, too
74 CIRCUIT & DESIGN IDEAS TV headphones amp, stereo delay unit
80 VHF/UHF SPECTRUM ANALYSER - 2 Construction and adjustment
90 AUTOMOTIVE ELECTRONICS Engine basics 4: emission control etc.

97 EXPERIMENTING WITH ELECTRONICS An electronic thermometer
104 VINTAGE RADIO RCA’s first TRF receiver — the Radiola 20

Professional Electronics

124 NEWS HIGHLIGHTS CSIRO develops multi-beam satellite antenna
128 NEW PRODUCTS Plain paper faxes, microwave sensor modules
132 T&M INSTRUMENTS FEATURE: The latest instruments available

136 MODERN RF SIGNAL GENERATORS - 2 Key performance parameters
140 T&M INSTRUMENTS FEATURE: New DMM, hand-held 1.3GHz counter
142 SOLID STATE UPDATE 280MHz bandwidth op-amp, fast 24-bit VGA
144 SOFTWARE REVIEW: DADISP 3.0 Data manager/display package
148 SILICON VALLEY NEWSLETTER Apple, Toshiba to develop new PDA
150 COMPUTER NEWS & NEW PRODUCTS Multi-media sound cards

Columns and Comments

4 LETTERS TO THE EDITOR Component supply problems, caller ID

5 EDITORIAL VIEWPOINT Never any shortage of ideas for projects...

40 FORUM A reader who's really put some speaker cables to the test!

112 INFORMATION CENTRE Looking further ahead, into the digital future
116 SHORTWAVE LISTENING New countries and new voices on the air
122 AMATEUR RADIO NEWS 35th JOTA this month, new club in Adelaide

Instruments, hard & soft

In this month's feature on test and
measuring instruments we look
mainly at free-standing instrument
hardware (see page 132), but there's
also details of new PC-based instru¬
mentation in the Computer Products
section (page 150), and a review of
the DADiSP software package, de¬
signed especially for manipulating,
reducing and plotting technical data
— like that from measuring instru¬
ments (page 144).

Magellan nears the end...

NASA's ‘ economy' spacecraft has
mapped Venus, and is now likely to
be scrapped — see page 20.

On the cover

Philips is no doubt hoping that its
new DCC-900 digital compact cas¬
sette recorder will be smiled upon by
the market as warmly as its advance
review sample was favoured by
lovely Donnah Estrella. Louis Chal-
lis reviews the DCC-900, starting on
page 12. (Photo by Greg McBean).

Departments

32 BOOK REVIEWS

120 EA CROSSWORD, HISTORY

121 MARKETPLACE

154 DIRECTORY OF SUPPLIERS
154 ADVERTISING INDEX
46 NOTES AND ERRATA

ELECTRONICS Australia, October 1992

MANAGING EDITOR

Jamieson Rowe, B.A., B.SC., SMIREE, VK2ZLO

FEATURES EDITOR

Peter Murtagh, B.SC, Dip.Ed.

TECHNICAL EDITOR
Rob Evans, CET (RMIT)

TECHNICAL CONSULTANT

Peter Phillips, B.E<±, Dip Ed., ECC

CONTRIBUTORS

Neville Williams, F1REE, VK2XV

Jim Lawler, MTETIA

Arthur Cushen, MBE

Tom Moffat, VK7TM

Peter LanKshear

SECRETARY

Ana Maria Zamora

PRODUCTION EDITOR

Mllli Godden

DRAFTING

Karen Rowlands

COVER DESIGNER

Clive Davis

PRODUCTION

Patrice Wohlnick, Mai Burgess
ADVERTISING PRODUCTION
Anthony Macarounas
CIRCULATION MANAGER

Michael Prior
PUBUSHER
Michael Hannan
ADVERTISING MANAGER

Selwyn Sayers (02) 693 9734
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The Australian Publication emblem on the front
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largely produced and edited In Australia, and
that most of the advertisements herein are the
products and services available within Australia.
ISSN 1036-0212

♦Recommended and maximum Australian retail
price.

LETTERS TO
THE EDITOR

Power relay project

With reference to the above project
(January 1992), I have found it to be very
useful with the home computer, but am a
little concerned that the project recom¬
mended using a five amp fuse for safety.
It is a well known fact in the electronics
world that semiconductors have a ten-
dancy to bum out before a fuse and with
three amp diodes in the circuit — you
guessed it.

This was proven when a 2400W heater
was inadvertantly plugged into the master
socket. Instead of the fuse blowing as it
should do, the diodes became a frizzled
mess, the box melted and, well, I wont’t
bother explaining the state of the PCB or
the fuse carrier. I therefore recommend
that perhaps a two amp fuse would make
the project a bit safer, in the case of the
odd mistake as explained above.

I do feel that this is a matter of impor¬
tance and should therefore be published
in the near future, even if for the sake of
safety.

Thanks for a great magazine.

A.J. Donald,

Glenfield, Auckland NZ.

Comment: We specified a JA fuse to
reduce the likelihood of ' nuisance' blow¬
ing during switch on, Mr Donald. How¬
ever, if your unit doesn't do this with a 2A
fuse fitted, by all means use the lower
rating for added safety.

Chip source

About 10 years ago, I purchased and
successfully constructed the (then cur¬
rent) ‘Playmaster Stereo Tuner’ kit from
Dick Smith Electronics.

Recently, the CMOS display driver
chip AY-3-8112 went defunct. I ex¬
hausted all efforts in trying to locate a re¬
placement, by contacting all your usual
advertisers, and whoever they suggested.

The question is obvious, I suppose: do
you know of anywhere that I may be able
to obtain the AY-3-8112 chip, or a suitable
replacement for same? Failing this, is it
possible to modify the circuit in some
way to use a different chip?

I am not very technically minded as far
as design is concerned, but I am en¬
thusiastic (and usually successful) in con¬
structing many of your kits — including
ALL of the early Paymaster Hi-Fi series.

You probably hear it often enough, but

seriously, keep up the good work with
your magazine (I’ll pay more for postage
IF I have to, too), as I have been reading
and collecting this magazine now for
around 30 years. Well done!

Gavin McLeod,

Comboyne, NSW

Comment: We don't know of a current
source of the chip, Gavin, but perhaps
one of the suppliers will see this letter and
provide this information. We'll try to offer
a substitute option, when time allows.

Amateur radio kits

In January/February 1990, EA publish¬
ed a long article on kits. Whilst some kits
from these manufacturers may no longer
be available, the article is still a good
starting point for anybody wanting to get
into kit construction.

As the Activities Officer for the Mid¬
land Amateur Radio Club, I plan to
present a talk in November on the current
state of play in the kit field. To this end, I
was wondering if you could bring me up
to date or perhaps put some of this letter
in ‘Letters to the Editor’, as kit producers
may wish to contribute to my planned talk
and consequently bring me up to date.

Many thanks and 73’s,

Dennis Fraser, VK3JHB,

PO Box 224, Kyneton, Vic. 3444

Westminister doorbell?

Would it be possible to consider a
project for an electronic door bell using
the traditional ‘Westminster chimes’?

I am familiar with the October 1988 ar¬
ticle, which is technically great. However,
I feel there would be a big demand for the
Westminister chimes, if this can be
managed electronically.

R. Wilkins,

Chapel Hill, Qld.

Comment: Well see what can be done,
Mr Wilkins. It doesn't sound too difficult
— but these things never turn out to be as
easy as they sound.

Also had trouble

I would like to add my confirmation of
the problems experienced by Mr Iain
Whyte (EA June, 1992).

I have found that several projects pub¬
lished in electronics magazines are im¬
possible to construct because the specified

ELECTRONICS Australia, October 1992

(or alternative parts) are impossible to
find in Australian electronics shops.

I have another complaint Some dealers
who advertise in electronics journals do
not reply to letters, even though I always
enclose a stamped addressed envelope for
reply. I can quite understand that many
young people would soon become disil¬
lusioned and frustrated and would be in¬
clined to abandon electronics as a hobby.

Henry Morley,

Horseshoe Bay, Qld.

Comment: Like Mr Whyte, you don’t say
which magazine projects you’ve had
trouble with, Henry. Hopefully not any of
ours, because we go to a lot of trouble to
check component availability.

Caller ID

I’ve just read Louis Challis in your
April issue. In his CES report, he seems
far more impressed by the prospect of
‘caller identification’ than I am.

‘Caller identification’ is itself mislead¬
ing. What is provided is the number from
which the incoming call was placed —
which may not tell you who is calling, if
the call is placed from anywhere except a
home phone. Being able to reject a call
without identification doesn’t sound all
that handy to me. Unless you recognise
the number (as an enemy, or a mother-in-
law), you have no idea whose call you are
rejecting. Maybe it was a prank call, or a
telemarketing call — but maybe it was
EA, saying you had won one of their sub¬
scriber competitions.

As for good reasons NOT to transmit a
calling ID, imagine the situation of a bat¬
tered wife phoning home from a woman’s
refuge to try to find out if the children are
still OK. Would she want the husband to
find out whose phone she is using? Or
someone calling one of the many ‘help
line’ services for distressed persons, for
drug abuse victims and so on. I can im¬
agine a variety of people who have
legitimate reasons not to want to provide
details of their home phone.

Business has the most to gain from
universal calling phone ID. I can see
Domino Pizza greeting you by name on
the third ring, and confirming that you
want the usual delivery order — no time
wasted getting an address or other details.
I also see effective information gathering
practices, if businesses can identify all
their callers. You and I can expect to have
some very accurately targeted advertising
and junk mail. Somehow I don’t find this
prospect all that appealing.

I do hope there is some debate on this
matter before we get the system all in¬
stalled.

Eric Lindsay,

Faulconbridge, NSW ❖

EDITORIAL

VIEWPOINT

Never any shortage of
ideas for construction projects!

I don’t know how many times I’ve been asked how we keep coming up with
the ideas for our electronics construction projects. Generally this seems to be
the first question I’m asked, whenever I meet any of our readers or someone
who looks through the magazine even casually.

The funny thing is that coming up with ideas for E4’s projects has never
been a problem, over the many decades we’ve been publishing. Quite the
contrary, in fact — most of the time, we have more ideas than we can possibly
ever develop!

Of course quite a few ideas come from you, our readers. Understandably,
many of you write in or send us a fax with details of projects you’d like to see.
These are all considered carefully, and if an idea seems both popular and
promising, at least one of us adds it to our list of ‘projects to work on’.

There’s also lots of feedback from many of our advertisers — especially the
firms who sell project kits and/or PC boards and other key components. The
people in these firms have very good contact with project builders, and they
soon get to hear which projects prove popular, which ones may have given
difficulty and which other project designs people have expressed a need for.

The kit and PCB firms are also good at letting us know when existing and
popular project designs may have become hard to build, due to parts being
dropped by manufacturers or suppliers. So in many ways they form an excel¬
lent ideas-gathering network — for which we’re very grateful.

And finally, there’s ideas from our contributors and ourselves. Most of us
are pretty steeped in the subject, and we’re constantly reading magazines,
application notes and other material from around the world. It’s amazing
how many ideas for projects are generated in this way alone, let alone the
other sources.

In short, then, there’s never any shortage of ideas for our construction
projects. The only real problems are to find the time to develop the
ideas into fully-fledged and tested designs, ready for publication — and then
to find enough space in the magazine, to fit in all of the information you need
to build them!

By the way this month, you’ll find details of a new protection module for
your expensive hifi speakers, developed by Rob Evans from the circuit he
included in his very popular Pro Series One Amplifier. There’s also the
construction details for Tean Tan’s flexible valve stereo amp and my own
spectrum analyser adapter — plus a simple electronic thermometer from
Peter Murtagh.

Next month we’ll have another batch of projects, from either our own
workbenches or those of our contributors. Electronics is such a constantly-
changing and exciting field that I’m sure we’ll never be short of ideas, for
projects to keep you interested in building your own equipment

Project building can be very satisfying, as well as allowing you to save a lot
of money. If you haven’t tried building anything as yet, I can warmly recom¬
mend it...

Jim Rowe

ELECTRONICS Australia, October 1992

What's New in

VIDEO and AUDIO

Lucasfilm Home THX
audio processor

The new Lexicon CP-3 Digital Sur¬
round Processor is a Lucasfilm Home
THX Audio system processor developed
to reproduce the same audio experience
of the finest motion picture theatres in the
home environment.

Pioneered by the studios that have
produced feature films like the Star Wars
and Indiana Jones series, the THX system
enables a home system to recreate the
magic of effects as well as sounds that
actually move with their visual sources.
Under development since 1980, the THX
system also permits the home theatre to

reproduce the full dynamic range of a
film’s soundtrack.

Using Dolby Pro Logic to decode and
‘steer’ surround sounds to their proper
locations, the THX system enhancements
in the surround processor provide addi¬
tional equalisation to achieve the proper
sound balance in the home, as well as
increased diffusion and envelopment of
the surround sound.

Lexicon has been named by Lucasfilm
to develop audio electronics for the
Lucasfilm Home THX Audio system.
The CP-3, the first product of this spe¬
cial collaboration is claimed to fully
deliver the initial promise of the home
theatre concept.

The CP-3 also includes sonic process¬
ing for the enhancement of any musical
recording to restore the acoustics of the
original performance environment, from a
jazz club to a symphony hall, a cathedral
to a giant rock arena.

While the CP-3 is designed to fully
complement the Home THX amplifiers
and loudspeakers, it is fully compatible
with virtually any audio equipment

For further information circle 184 on
the reader service coupon or contact
Audio Insight, Unit B, 5 Skyline Place,
Frenchs Forest 2086; phone (02) 975
3011.

JVC, Hughes making
big screen HDTV

Japanese firm JVC is to develop a con¬
sumer version of a special high resolu¬
tion, high brightness LCD colour TV
projector originally developed by Hughes
Aircraft in California. The Hughes
projector is said to provide resolution
higher than that for HDTV from an LCD
panel 50mm wide, with a projected image
that is easily viewed in normally lit rooms

Dolby-S cassette
deck from Teac

The recent release by Dolby
Laboratories of its new Dolby S noise
reduction system allows analog cassette
decks to meet the challenge of the digital
recording format. Taking advantage of the
new technology is Teac, which recently
announced its first Dolby S, three head
cassette deck to the Australian market.

The Teac V-8000S is one of the first
cassette decks to incorporate Dolby S, in
addition to the more familiar Dolby B,
Dolby C and Dolby HX-Pro headroom
extension system. Since the Dolby S cir¬
cuitry has (at the time of printing) not yet
been compressed into a single VLSI chip,
its inclusion has imposed a significant
premium in manufacturing costs. The
Dolby S electronics in fact occupies a
major part of the amplifier’s circuit board.

Dolby S provides more than 20dB of
noise reduction in the middle/high fre¬
quencies where tape hiss is most objec¬
tionable. It achieves this performance
with technology that minimises the pos¬
sibility of audible side effects. Dolby S

6 ELECTRONICS Australia, October 1992

has evolved from techniques used in the
widely acclaimed Dolby SR (Spectral
Recording) system. Unlike Dolby C,
Dolby S also adds lOdB of noise reduc¬
tion in the lower mid range where nor¬
mally mid range ‘blurring’ or ‘grundge’
often detracts from the clarity and
smoothness of the reproduced sound.

The V-8000S is designed with user ad¬
justable bias, tape sensitivity and in¬
dividual channel calibration controls are
situated to the right of the centre mounted
cassette well. This enables adjustment
for the variations of tape formulation

within the same tape type. It also incor¬
porates a CD direct input, CD level
check, electronic linear tape counter,
ON/OFF display, CD synchro connect
(when used with other Teac components)
and an infra remote controller.

The V-8000S is covered by a five year
parts and labour warranty, and is avail¬
able at selected Teac dealers and depart¬
ment stores.

For further information circle 182 on
the reader service card or contact Teac
Australia, 106 Bay Street, Port Mel¬
bourne 3205; phone (03) 646 1753.

even when expanded to 10m across. The
Hughes projector does not operate in the
same manner as other LCD projectors,
with a matrix of electrically-controlled
pixel cells; instead it uses an optical sys¬
tem to focus an image from a CRT screen
onto a special panel having an amorphous
silicon layer, a dielectric mirror and an
LCD layer sandwiched together between
transparent electrodes.

The LCD panel then acts as a ‘image
light valve’, modulating light from a high
intensity lamp.

At present the projector requires three
CRTs and three panels — one per primary
colour — for full colour images, but
Hughes is apparently working on an im¬
proved version which allows the three
colour images to be time-multiplexed via
a single panel. This uses direct electrical
imaging on the LCD panel, using a wafer
of single-crystal silicon.

High quality
speakers from Qld

Queensland loudspeaker manufacturer
Star Acoustics, based on the Gold Coast,
has released a range of locally made
high quality speakers using a novel trian¬
gular prism-shaped enclosure which in¬
hibits internal standing waves and also
provides greater rigidity than convention¬
al enclosures.

The systems all use hardwired cross¬
over systems with very heavy gauge
matched air-cored inductors and quality
polypropylene capacitors.

Smallest system in the range is the
Symphony, which uses a 125mm Focal
midrange driver with a 25mm dome

New Distributor
for Celestion

Amber Technology has been appointed
as the exclusive Australian distributor for
Celestion International Ltd., of the UK,
manufacturer of high performance
loudspeaker systems and components.

New mini system
from Kenwood

Kenwood’s new UD-300 mini com¬
ponent system is designed for home, of¬
fice or study environments. It combines a
25 watts per channel amplifier/ seven
band graphic equaliser/spectrum analyser,
AM/FM stereo tuner/double cassette
deck/CD player, and 45 watt, two way
speakers. Special features include
presence modes that can accentuate the
critical mid-range frequencies for a more
‘lively’ musical ambience.

Additionally, the seven band graphic
equaliser allows customised tailoring for
different acoustical room environments
with convenient memory presets for most

tweeter and sells for an RRP of $1698.
Then comes the Dynamics, which has a
200mm woofer and a tweeter level con¬
trol to allow balance adjustment for per¬
sonal taste or to match the environment,
and with an RRP of $1998.

Next in the range is the Concerto, in a
floor-standing cabinet lm high and with a

Amber’s professional audio division
will distribute the extensive range of
Celestion professional loudspeakers to
the OEM, public address and retail
music markets.

The complete Celestion range will also
be marketed by Amber’s network of
specialised audio retailers.

often used settings. Versatile karaoke
facilities include Mic Mixing and Hit
Master function. The Hit Master function
will effectively cancel the vocal portion
of the music enabling the user to sing
along with a ‘karaoke’ effect.

The heart of the UD-300 mini com¬
ponent system is the combined A-AB
amplifier/graphic equaliser/spectrum
analyser that offers 25+25 watts RMS. A
motorised volume control is used, which
is claimed to be superior to the noisier
electrical type. The amplifier also offers
Kenwood’s NB (Natural Bass) circuit and
a sub-woofer output

The UD-300 is covered by Kenwood’s
three year parts and labour warranty and
has a recommended retail price of $1299.

175mm bass-midrange driver and a kev-
lar inverted dome tweeter (RRP $2398).
Top of the range is the Maestro system,
which combines a 200mm polykevlar
woofer, a 125mm neoflex midrange and a
30mm kevlar inverted dome tweeter in a
1200mm high three way phase-linear bass
reflex system (RRP $7498).

Further information is available by cir¬
cling 181 on the reader service card, or by
contacting Star Acoustics, PO Box 158,
Bond University, Gold Coast 4229; phone
(075) 75 2704.

‘Pro Series’

NiCad dischargers

For full capacity and longest working
life, NiCad battery packs need to be
deeply cycled. Often a discharger unit
is required to ensure full discharging
before the pack is re-charged. The new
Keene Electronics ‘Pro Series’ of dis¬
chargers is designed to suit the NiCad
packs used in Sony, JVC, Sanyo and
Canon camcorders, and will discharge
packs faster than the standard range while
still cutting off accurately at the correct
voltage of 0.9V per cell.

All models in the Pro Series range are
covered by a three year warranty. They
are available from VideoCam Acces¬
sories, PO Box 2000, Strawberry Hills
2012; phone (02) 698 1470. ❖

ELECTRONICS Australia, October 1992

“I can see clearly, now!”

New Australian
anti-glare process

An Australian firm has developed a new process for removing reflections from the screens of TV
sets and computers, and independent tests have shown it to be surprisingly effective.

by BARRIE SMITH

I have always been intrigued by the
conflicting demand that a computer
screen is required to show high resolu¬
tion displays, aided by little or no reflec¬
tion from the screen’s surface, while the
domestic TV receiver has perpetually
suffered from a mirror-like surface that
(until recently) was also grossly curved.
The combination has always made en¬
joyable TV viewing in the daytime
something of a challenge.

While touring a TV receiver factory
recently, I asked why the latter type of
display had never received the same
anti-reflection treatment afforded the
computer screen. The answer was ‘we’re
working on it’.

Well, it turns out that the factory itself
(Panasonic) was not working on it —
S but a Brisbane company has in fact
produced a treatment, and the latter
company contacted me with information
about their process.

Now many companies — like
Panasonic — are considering its intro¬
duction to their products and assembly
lines.

Eye strain

A poll quoted in the Wall Street Jour¬
nal (19/11/91) revealed that 47% of of¬
fice workers cited eye strain as a serious
concern. More specifically, the
American Optometric Association
reported its members see more than
eight million VDT-related eyestrain
cases a year. Some 37% of these were
directly attributable to factors such as
screen glare and poor lighting or screen
resolution.

In response, an optical coating com¬
pany announced that sales of its anti
glare filters have climbed by more than
50% in the last three years. Apple Com¬
puter, among others, uses an anti-glare
treatment on its displays which scatters

8 ELECTRONICS Australia, October 1992

Computer screens at the offices of Brisbane City Council were given onsite
treatment using the Vision-Clear formulation. Oscilloscopes, depth sounders,
and many other displays can all benefit from the process.

light and provides control of brightness
and contrast.

No figures are available on glare-in¬
duced eyestrain in home TV viewing.
However, it is estimated there are cur¬
rently nine million TV sets and two mil¬
lion computer screens within Australia
— so an answer or cure for the problems
of screen reflection would in itself be
not only a technological advance in
terms of eye health, but constitute a
product of considerable commercial
potential.

Brisbane company Vision-Clear

Marketing, after handling a European
anti-glare product, realised the potential
of such a treatment. Due to supply and
cost problems importation was ended,
but steps were taken to develop a local
process that would surpass it in effec¬
tiveness. This took place in the late
1980’s, and was marketed in a limited
fashion in Brisbane.

In the last year, redevelopment was
undertaken to conform to changes in the
propellants allowed to be used, under
ozone protection requirements — and to
adjust to changes in computer technol-

Onsite treatment of a domestic TV screen. An odour is given The experimental set up used to compare the reflected light
off but this has been minimised by adding a deodoriser to from glass which had not been coatedwith that given the
the Vision-Clear formulation. two kinds of Vision-Clear treatment.

ogy. Expenditure reached the vicinity of
$150 - 200,000, due to the close
parameters required in the manufactur¬
ing process.

Formally known as LC008 Clear Anti-
Glare Aerosol Lacquer (Patent Pending)
the product is supplied ready for use in
an aerosol can.

The chemical content includes
petroleum hydrocarbon, acetone, ester
solvents, methyl iso-butyl ketone, al¬
cohols, resins/plasticisers, nitrocel¬
lulose, surface treated silicon dioxide
and other additives.

Two grades are manufactured —
standard, for TV sets, and a grade for

computer and similar displays which
preserves the higher resolution of the
latter screen.

LC008 can be used not only on
TV/computer displays, but also digital
readout panels, X-ray units, oscillo¬
scopes, depth sounders, laptop screens,
register and teller units. Units with non¬
glass screen surfaces are usually fitted
with an acrylic laminate — the latter
being treated with the coating so as to
allow replacement — as the coating can¬
not be removed from this type of sur¬
face.

Once applied, its major advantage is
that it allows the display screen to be

placed virtually anywhere, without need
for drawn curtains or closed blinds. Out¬
side viewing is also possible.

The application process is reasonably
simple, once the screen is cleaned and
the screen surround masked. The coating
is then simply sprayed on, as evenly as
possible.

Approximately four to six
screens/hour can be coated by one ser¬
vice person, dependent on the unit’s
location within the site and the number
of service personnel used.

An odour is given off, but this has
been reduced by adding a deodoriser to
the product Vision-Clear is non-toxic in
the amount used, but applicators do use
a surgical nose and mouth mask when
coating a number of screens. The
product is only available as a ‘service
supplied’ product mainly due to the
demands of the application process.

Under normal use the life span is in¬
definite. While guaranteed for five years
— under certain conditions — the coat¬
ing can be damaged by scratching with a
metal object or some solvent liquids.
Cleaning is by means of a soft damp
cloth.

Visually, the coating is matte. In most
cases approximately 10% definition loss
is experienced, but it is possible to
reduce this to about 5%. The company
claims an average person would have
difficulty in determining the difference.
Interestingly, the curvature of a coated
screen does not substantially affect the
degree of reflectivity...

Independent tests

The company contracted the Physics
Department of Queensland’s University
of Technology, to test the system. The
results are enlightening.

The tests were conducted in the
Physics Dept’s Photometric Laboratory.
Measurements were made by shining a
standard incandescent light source onto

Sample

Angle of Incidence

Reflected

Luminance

Percentage

Reflectance

Uncoated

10 °

0.291

100

20 °

0.340

100

45 °

0.474

100

TV(N)-1

10 °

0.012

4.1

20 °

0.020

5.9

45 °

0.023

4.9

TV(N)-2

10 °

0.012

4.1

0.021

6.2

45 °

0.022

4.6

VDU(N)-1

10 °

0.055

19.0

0.080

23.5

45 °

0.096

20.3

VDU(N)-2

10 °

0.056

19.3

0.081

23.8

45 °

0.096

20.3

The results obtained by the Physics Department of Queensland’s University of
Technology are tabulated here. Note that the ‘TV’ formulation gives a higher
degree of glare reduction than the ‘VDU’ formulation.

ELECTRONICS Australia, October 1992

READER INFO NO. 4 2

CHRISTIAN
BUND MISSION

1245 Burke Rd.,
Kew 3101

VINTAGE RADIO

Circuits, Components,

Radios, Loudspeakers
VALVES - Audio, Radio, Industrial
BOUGHT - SOLD - TRADED
Send SSAE for Catalogue

RESURRECTION

RARIC

51 Chapel Street Windsor Vic 3181
Tel (03) 529 5639 Fax (03) 521 1950

“/ can see clearly, now!”

glass samples coated with the product.
Light source colour temperature was
2850K (+/-50K). The illumination was
‘coned’ to a diameter of about 25mm —
to concentrate the light source at a
central point on the test samples.

The amount of reflected light was
measured at differing angles of in¬
cidence, using a calibrated, spot reading
light meter, in photopic response range
and with a cosine adaptor attached.

Final assessment of the test results
used the ratio of reflected light from the
coated sample to that from the uncoated
one, and the Figure based on the degree
of relative percentage reflectance.

The samples used were:

1. An uncoated, clear sheet of glass.

2. Glass sheet — TV (N) — coated
with the TV formulation spray.

3. Another sheet of glass — VDU (N)

— coated with the computer stand¬
ard spray.

TV (N) refers to Television Neutral,
VDU (N) refers to Visual Display Unit
Neutral.)

Two same size samples of each of the
glass pieces were supplied to the
laboratory. Measurements were made at

10, 20 and 30 degrees of incidence. The
results in the table can be interpreted by
deducting the percentage reflectance fig¬
ure from the TV (N) or VDU (N) from
the uncoated sample, i.e., 100% - 4.1% =
95.9% effective reduction at 10 degrees.

It’s worth noting the difference be¬
tween reflectivity of the VDU (average
21%) and the TV samples (average
5.8%) — the latter being coated with the
lower resolution standard spray.

Market potential

Obviously, with an installed base of
millions of TV sets and computer
screens, the Australian market looks
most attractive. However, believing
themselves to be ‘on a good thing’, the
company is currently negotiating with a
North American company for manufac¬
turing, distribution and marketing. It is
believed there is no substantial opposi¬
tion product in that market. Talks are
also being held with TV manufacturers
and suppliers — Sharp, Sony, Panasonic
and other majors — plus retail outlets.

The future for Vision-Clear is ob¬
viously looking ‘bright’ — with a low
value of reflection! Further information
is available from Vision-Clear, 4 Park
Road, Milton Qld 4064; phone (07)
367 1602, fax (07) 367 0436. ❖

$ 3 . 2.50 (NZ $18.00 Incl GST) NDD

4 E H GFtE/VT VE/VR!

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ELECTRONICS Australia, October 1992

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READER INFO NO. 4 3

Video & Audio: The Challis Report

THE PHILIPS DCC900
DIGITAL CASSETTE RECORDER

Early next year, Philips is planning the Australian release of recorders and software for its new DCC (digital
compact cassette) system. However this month Louis Challis had the opportunity to run his instruments
and educated ears over the first production sample to reach our shores, of the new DCC900 'high end'
DCC recorder. So here's what you can expect, around February or March...

As I sit here listening to Charles Dutoit
conducting the Montreal Symphony Or¬
chestra in their rendition of Bizet's 'L'-
Arlesienne Suites', I have a strange feeling
of deja vu. My memories slip back to
the year 1955, for it was then as I
clearly recall, that I purchased my first
10" 33rpm long play recording. The title
was, as you may well have guessed,
Bizet's 'L'Arlesienne Suites' — the only
difference being the conductor (Sir John
Barbirolli) and the orchestra (the famed
Halle Orchestra).

So it is indeed fitting that the first pre¬
recorded Digital Compact Cassette (DCC)
that I should play on the new Philips
DCC900 Recorder should be that very
same piece of music which initiated me to
the real joy of LP records, and once again
stirs new emotions as it heralds yet
another monumental change in the way
that you and I will listen to our music.

12 ELECTRONICS Australia, October 1992

It is little more than 18 months since
Philips announced its auspicious decision
to market DCC. In the intervening period,
they have taken this bold and revolution¬
ary new concept from what I originally
observed by way of far from perfect
prototypes, all the way through to the ini¬
tial run of production machines which
they initially promised would be in
Australian stores before Christmas.
(Editor's Note: Now it looks like February
or March , before there will be enough
production to supply Australia.)

The DCC system has now been
developed to the point where the very first
production machine to reach EA for
review is an extremely sophisticated and
powerful competitor for DAT, which it will
eclipse — solely because it is has the sup¬
port of the software companies, which are
providing the pre-recorded media so criti¬
cal for the success of this kind of product.

Of course, most of us in the business
realise that DCC still faces a very real
threat from the equally potent Sony Mini
Disc system. And it may yet face an on¬
going healthy competition from the
original Philips Compact Cassette, (both
in the pre-recorded and blank format),
which it will only slowly displace in the
market place.

But what is DCC, and in what way does
it pose a threat to the other systems? More
importantly, why can't all these different
systems live together in harmony?

The background

For answers to such questions, we
really have to go back a full century in
time to the end of 1880's and the begin¬
ning of the 1890's.

It was then that Thomas Alva Edison
developed his cylindrical records, and
dominated that brand-new market for

most of and certainly the early part, of the
next 20 years.

At almost the same time as Edison
developed his wonderful invention
(within a year, in fact), a most unlikely
inventor by the name of Emile Berliner
invented what was then perceived to be
an equally unlikely, but most competitive
product: the now famous disc recording
system, which only toy manufacturers had
any real interest in until just before the
turn of the century .

Initially Emile Berliner had a tough time
competing with Edison, but within a
decade their respective positions had
reversed and the public, (and the licen¬
sees manufacturing their respective
products) had rejected the Edison 'rolls' in
preference to the Berliner disc recordings.

There were obviously a number of
reasons for that rejection, but the most im¬
portant then, and what I perceive to be
equally important today, was that nasty
economic factor. At the time it was the
cost of manufacturing the Edison rolls.
Berliner's disc recordings could be
stamped out in the twinkling of an eye,
and mass-produced far more cheaply than
could the Edison rolls. In much the same
way the Berliner record players did not
require the fine and careful tolerances of
the mechanical lead screws, on which
each Edison reproducer was entirely
dependant. The result is now history, and

the public had voted for the better and
more practical system, with their money.

As I see it, in the end the public knows
what it wants, and although it is often
fickle and obviously nurtured by advertis¬
ing hype, it generally sees through the fog
of blarney in the end and comes to its
own intuitive and/or considered opinion.

Now there are very potent and similar
parallels that may yet be drawn in the
next year or so, between the Philips DCC
system and the Sony Mini Disc system.
However those issues and a discussion in
depth is more appropriate in a later
review, and particularly when it is backed
by all the pertinent facts.

At the end of World War II, the wonder¬
ful German invention of magnetic tape
recording took the public by storm, as it
gave those of us who could afford it the
opportunity to record what we wanted to,
when we wanted to. But there were plenty
of vexing user problems with the original
reel-to-reel tapes and recorders, which
Philips understood only too well, and
were taken into good account when they
developed the Compact Cassette system
in 1963.

Now although Philips had invented the
concept, and controlled almost every
aspect of its subsequent use, they inex¬
plicably extracted no royalties from any of
the subsequent recording equipment or
blank compact cassette manufacturers.

Their only requirement was that the users
should strictly conform to their (Philips)
technical standards in all respects.

Very laudable, you may think! Well yes,
it was — except that by so doing, they
missed out on what I would guess to be
somewhere around $5 billion in royalties.
Which even nowadays can't really be
scoffed at — particularly if you look at
Philips' published global profit and loss
balances, for the last few years.

When Philips and Sony developed what
I perceive to be the most important hifi-re-
lated invention of the 80's, namely the
CD, the accountants in their respective
firms presumably whispered in their
respective directors' ears quite early in the
piece, and as a result the name of the
game became 'Licensing Royalties'. And
this policy has been quite evident ever
since. So nowadays it's not how many you
sell that matters, but rather how many
everybody sells that determines how well
you do in the end.

Needless to say, after investing count¬
less millions of dollars in the development
of DCC, (once more all by themselves),
the accountants and top management at
Philips decided to apply the same for¬
mula. The problem was that to get DCC
accepted by the rest of the world, Philips
needed some other strong players in its
team to convince everybody else that they
had the 'muscles to Win'.

Inside the DCC900. Most of the critical circuitry is hidden under the shield plate on the left , although some of the digital
processing circuitry is visible on a small PC board just at the back of the central transport deck.

ELECTRONICS Australia, October 1992

THE CHALLIS REPORT

As it happens, Sony wasn't prepared to
be in the front line of the Philips team, as
they earnestly believed that their own
Mini Disc had more pluses and that it
would eventually become the preferred
system — or put more bluntly, the system
that the public is going to vote for. So
when Sony would not join the team,
Philips did a deal with Matsushita, Sony's
arch rivals, and in exchange for some very
attractive financial inducements, Mat¬
sushita and its affiliates fronted up behind
the captain, so that the heavies were there
to support in the ruck.

The new cassettes

Now that you understand the back¬
ground, it's about time we talked a bit
more about the product, namely DCC.
Philips decided to integrate the best fea¬
tures of the tried and proven compact cas¬
sette into an entirely new digital system.
So DCC uses a cartridge which is a cross
between a standard compact cassette
(with almost identical external dimen¬
sions), and the key packaging elements of
a 3.5" floppy disc (which as it happens
was developed by Sony). That particular
Sony related design element is the neat
dust-exclusion shutter — as dust happens
to be one of the most potent and
dangerous enemies that the new Digital
Compact Cassettes will face.

As access and spooling is all controlled
from the one side, the other face of the
cassette is perfect for fancy artwork, and
of course that's precisely what they have
elected to provide. The design also picks
up the detection tab concepts of the com¬
pact cassette by way of a series of indents
(or holes), so that the DCC recorder/player
knows how much tape is on the cassette.

Because of the unusual high frequency
data requirements, the tape is a video for¬
mat chrome or cobalt doped ferro-oxide
coating, whose thickness is less than four
microns (um) and whose width is a con¬
ventional 3.76mm. Each tape on the cas¬
sette has an A and B side, but instead of
turning the cassette over, the heads rotate
to provide access to both halves of that
miniscule 3.76mm wide coating.

The digital signal is recorded on eight
parallel tracks, each of which is only
185um wide — out of which only a tiny
70um is actually scanned during
playback. The difference of 115um is ac¬
tually a safety factor to reduce the sen¬
sitivity to azimuth error. There is a ninth
track on each side of the tape, on which
(subcoded) information relating to the
data display and related control functions
are recorded.

With such small track widths, and with
an obvious mass production requirement,
conventional recording heads were ob-

14 ELECTRONICS Australia, October 1992

viously out The designers had to develop
cost-effective recording and playback
heads with really subminiature dimen¬
sions, suitable for this application. That
was obviously no mean feaL

The DCC heads then had to be similarly
matched by a pair of compatible analog
playback heads, specially designed for the
standard compact cassette and which
could also be rotatable so as to cover both
sides of a standard compact cassette — as
these would need to be played for some
time in to the future.

Philips met both needs by drawing
upon its experience in transistor and 1C
manufacturing techniques, and using
thin film technology to produce two en¬
tirely different types of recording and
playback heads. Very little has yet been
said about the integrated recording head
technology, which will be worthy of an
article in its own right By contrast, the
magneto-resistive playback heads are at
least described in general terms in Philips'
preliminary literature.

With a system as complex as this, one
of the most sensitive issues which the
designers had to address was the problem
of tape alignment, as any errors in
azimuth or track alignment would quickly
destabilise things and result in total failure
of what would otherwise have been a well
conceived system. The tape alignment
techniques which they finally adopted
were innovative and relatively simple.
The head incorporates a fixed azimuth
tape guide, through which the upper edge
of the tape is gently forced against a (har¬
dened) reference surface, to ensure that
the alignment is positive.

The edge of the tape is forced against

the guide by using a sloped lower face at
the base of the head assembly. The result¬
ing curvature of the tape forces it up
against the upper reference surface, and
the curvature of the tape stiffens the mag¬
netic surface and simultaneously forces it
against the heads — so that no compli¬
cated pressure pads are needed. Provided
the edges of the tape have been cleanly
and neatly slit, then the alignment is posi¬
tive and nigh-on perfect

Compression needed

As you may well realise, even with
eight parallel data tracks, it's not
possible to encode linearly two high
quality audio channels, with data being
sampled at anywhere near the 32kHz,
44.1kHz or 48kHz sampling frequencies
for which this system has been
designed. When you add the complica¬
tion of error correction data, and other
special requirements which this system
uniquely imposes, something has to be
discarded as this format simply can't cope
with this amount of data.

Philips realised this very early in the
piece, and called in their own acoustical
consultants, who developed the 'Precision
Adaptive Sub-Code' (PASC) digital coding
and compression system.

The basic underlying concept behind
this PASC coding is that the audible fre¬
quency spectrum with which we hear
may be divided in to a series of critical
bands, and each of those individual
bandwidths can appropriately mask the
sound energy in adjacent bands provided
the level of the dominant band is ap¬
propriately greater than the level in the
adjacent band. In addition there are a

The recorder has a roll-out tray rather like a CD player. The DCC cassette Is
located accurately in the tray by suitable guides.

The rear panel has the expected array of Input and output connectors — plus a
few extras. These include variable analog outputs as well as fixed, both coaxial
and optical digital inputs and outputs, and two ESI remote control connectors.

range of frequencies and related sound
levels, defined by a curve which is techni¬
cally known as the 'normal threshold of
hearing', below which most people (apart
from a few), cannot normally hear.

The acousticians at Philips realised that
if one were prepared to go far enough in
making use of the principles of masking in
a sensible and systematic manner, and
simultaneously adopt the principle that
sound levels below the threshold of hear¬
ing can similarly be excised, then you
could cut down the data to be recorded
by more than 75%, without the listener
being aware of this deletion.

Of course that's exactly what they did.
And as I have proven to myself in much
the same way that you will soon be able
to prove to yourselves, you just don't hear
any difference. The reason being that the
PASC system expeditiously calculates the
thresholds of dynamic audible perception
during its analysis and signal encoding
process, so that the encoded data requires
less than 25% of the data bit rate capacity
of a conventional PCM (Pulse Code
Modulation) system.

Yes, this is certainly 'cheating', but I
can assure you that it is nonetheless
aurally legitimate — and more important¬
ly, it works! This was virtually the only
way that Philips could make eight
parallel heads encode or decode the digi¬
tal data and still retain the same critical
tape speed of 4.76cm/s — and hence the
same tape playing times as analog com¬
pact cassettes.

At last, the DCC900

The DCC900 is the first of the new DCC
recorders, and as a high-end model it is
radically different in its visual and func¬

tional concepts as well as in its perfor¬
mance potential when compared to the
simple compact cassette recorders with
which we've become so familiar over the
last 25 years.

The most obvious difference is the num¬
ber of new control functions which it in¬
corporates. The most significant of these
are located on the left hand side of the
front panel, identified by the label 'Marker
Controls'. There are six of these pushbut¬
tons, in two groupings, which provide
similar functions to those which have
been developed for the DAT system.
These include an Auto Start Marker,
which may be selected on or off, and a
Start Marker Write for manually recording
a start marker at the start of each new
track of music.

Then there's the Renumber button, for
checking through the complete tape and
correcting those numbers which may be
out of sequence. The residual marker con¬
trols relate to the Auto Reverse Mode and
these include the Next Marker Write, for

writing the next marker in sequence; and
Reverse Marker Write, for writing a revers¬
ing marker so that the tape will reverse at
that point; and lastly Marker Erase, for
erasing a marker at that specific location.

If these controls and their descriptions
appear somewhat alien and an unneces¬
sary complication, let me re-assure you
that they are only required if you intend to
carry out your own recording and you
wish to provide the same flexibility in
terms of rapidly finding individual tracks,
in precisely the same way that you are
able to with pre-recorded software.

The average older person, who is less
skilled at handling new equipment of
this type, will more than likely purchase
pre- recorded cassettes and so avoid the
need to master a new technology with its
associated new language. (This has been
the trend in America with such equip¬
ment, and I have no doubt it will prove so
in Australia).

Below the marker controls are the main
power switches, the optional timer
switches and a Dolby switch, through
which Dolby B and C may be selected
when playing standard analog cassettes.

On the right-hand side of the panel
there is a reasonably large and ap¬
propriately labelled pushbutton for open¬
ing and closing the cassette loading tray,
adjacent to which is a large recording
level (volume) control, which is sensib¬
ly placed directly above a smaller
balance control.

Adjacent to these controls is the input
selector switch, by means of which you
select conventional analog inputs/digital
inputs or optical inputs from external line
inputs — which would typically come
from a CD player, DAT recorder, CDV
player, FM radio or whatever.

On the two outer and upper edges of
the recording tray, there are four pushbut¬
tons. These respectively provide Counter
Reset for resetting the tape counter; a
Repeat button, which has three modes
which are cyclically selected and which
allows you to repeat the current track,
repeat all tracks, or to disable the func-

A close up shot with the recorder’s cover off, showing the special thin-film head
assembly. This rotates through 180 degrees to record/play the second half of a
tape, removing the need to turn over the cassette.

ELECTRONICS Australia, October 1992

THE CHALLIS REPORT

tion; a button labelled Text which allows
you to display the album's title, track title,
the artist's name, the total number of
tracks on the tape, and the time into
the tape (by sequentially activating the
button so that the display identifies
itself and then provides the generally
abbreviated text identification); and the
Time button, through which you can
select the different time modes provided
— which are respectively absolute time,
track time, remaining time and the
normal counter mode which is presented
directly in seconds.

At the bottom of the deck a shallow
sloping panel incorporates the normal
tape recorder playback controls, as well
as record function controls. As I noted,
there are some unusual record controls,
the first of which is Append, which sear¬
ches for a recording position on the tape,
and which when finally found, then ac¬
tivates the Recording Pause mode.

The time to find this position on the
track was significantly longer than I would
have expected (or would have liked), and
as I soon discovered, the recording button
can only be activated after you have
selected and activated the Append switch,
which was a trifle confusing at first Two
other conventional controls provided in¬
clude a Record Mute, for recording silent
passages, and last but not least a CD Sync
switch, which facilitates automated and
synchronised recording from your CD
player — provided it has a matching ESI
bus socket and control circuitry (about
which I will have more to say later).

In the middle of the recording tray is an
extremely comprehensive and well con¬
ceived multi-coloured fluorescent display,
which formats its peak reading bar-graph
type meters so as to conform to the tape
format which has been loaded.

Thus by way of example, in the DCC
mode the recording display has its top
level set to zero VU, above which the red
overload light is rapidly activated — as
unlike a conventional analog compact
cassette, DCC will not tolerate excursions
beyond that level. When a conventional
compact cassette is loaded however, the
DCC900 immediately recognises the
change in format, and the display has the
zero VU displaced down by 10VU points
to the left In this mode the display's top
level changes to +10VU, in conformity
with normal compact cassette practice.

The only other controls on the front
panel are the headphone volume control
and a 6.5mm stereo socket for head¬
phones on one side, and a somewhat in¬
nocuous infra-red detector for the
excellent remote control with which the
DCC900 is supplied, on the other.

On the back panel there are 10 coaxial

PHILIPS DCC90G-
CASSETTE ^
RECORDER

ANALOGUE
INPUT
RIGHT TO
RIGHT

9 -30VU

DATE 9-8-92

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PHILIPS DCC900--
CASSETTE
RECRODER *3

ANALOGUE

INPUT

RECORD TO 1
REPLAY

DATE 9-8-92 -

00 1000 3000 MOO 10000 700(

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PHILIPS DCC900
CASSETTE
RECORDER *3

RECORD TO
REPLAY
FREQUENCY
RESPONSE *1

WITH DIGITAL
INPUT 0

AT OVU

-1

DATE 9-8-92

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PHILIPS DCC900
CASSETTE
RECORDER 0

REPLAY
FREQUENCY
RESPONSE WITH
TYPE 1 _ 10

REPLAY AU

REFERENCE
COMPACT
CASSETTE TAPE

9 20VU " 20

DATE 9-8-92

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REPLAY
FREQUENCY
RESPONSE WITH
TYPE 2 -10

REPLAY
REFERENCE
COMPACT
CASSETTE , n
TAPE " 20

a -20VU

The main response plots obtained for the DCC 900. The three uppermost curves
show the excellent digital record/play response , with both analog and digital
inputs, while the lower curves show the rather disappointing analog performance.

ELECTRONICS Australia, October 1992

Measured Performance Of The Dec Digital Compact
Cassette Recorder - Model No.DCC 900
Serial No. MZ 01920601087

1. Frequency Response

Record to Replay Digital input

5Hz to 20kHz +/-

O.ldB

Analog input

2Hz to 22kHz +/-

0.2dB

Linearity

Nominal

Left

Right

Record to Replay at (1kHz)

Level

Output

OdB

0.0

-1.0

-3.0

-2.9

-6.0

-5.9

-10.0

-9.9

-20.0

-30.0

-29.9

-40.0

-39.9

-50.0

-51.2

-49.9

-60.0

-60.3

-61.2

-70.0

-69.9

-69.4

-80.59

-80.4

-89.3

-85.24

-83.8

-84.7

-89.46

-89.0

-89.7

Channel Separation

Frequency Right into

Left into

Left dB

Right dB

100Hz

1kHz

10kHz

4. Distortion (@ 1kHz)

Level

2nd

3rd

4th

5th

THD%

-87.2

-103.0

-111.5

0.0044

-10

-89.2

0.0039

-30

-80.4

0.0096

-40

-71.4

-73.2

-72.9

-75.6

0.045

-50

-61.7

-64.9

-62.9

0.112

-60

-57.4

-48.0

0.42

-70

-40.4

-52.6

-45.5

1.12

-80

-39.8

-38.9

-37.7

-35.0

2.7

-85.24

-37.5

-27.5

-35.7

-20.1

11.0

-89.46

-26.4

-13.9

20.0

-91.24

-23.2

-8.9

-19.2

-13.9

43.0

Replay Frequency Response with Standard Compact Cassette.

Type 1 Tape 30Hz to 5kHz + 0 -3dB

Type 2 Tape 40Hz to 5kHz + 0 -3dB

sockets, plus two optical connections,
which are an unusually large number of
connectors for a consumer-orientated tape
recorder. These include a pair of variable
outputs (whose output level is controlled
by the remote control), two outputs with
fixed level, a pair of line input sockets, a
coaxial digital input socket and a match¬
ing coaxial digital output socket to serve a
digital amplifier or other suitably con¬
figured equipment The two optical sock¬
ets are designed for connection to digital
equipment such as CD's, DAT's, CDV's, or
satellite tuners for input, or conversely to
a digital amplifier for the digital output
Last but not least are two sockets,
through which the ESI (or Enhanced Sys¬
tem Intelligence) remote control may be
connected. This is in effect a somewhat
contradictory feature, as the designers
have elected to make it easier for you to
automatically record tapes from your CD
player or other equipment with what
would be best described as 'one step, two
switch functional control' — so that you
can produce perfect tapes without even
the need to adjust your volume controls,
and thereby have perfect tapes each time.

This approach is even more simple than
you think, in that all the relevant coding
information is automatically transferred to
the tape; you don't have to even mark
your start and finish ID's.

The inside of the unit is very solidly
constructed — a hallmark of Philips' con¬
servative design philosophy — and the
printed circuits are loaded with LSI and
conventional 1C chips. I anticipate that the
second generation of DCC recorders will
use significantly fewer and I suspect sig¬
nificantly larger chips, to simplify the
electronics design.

Objective testing

Having whetted my appetite, I
proceeded to put the first DCC recorder to
reach Australia through its paces. My first
and most critical observation was the al¬
most unbelievably flat and broad frequen¬
cy response that the DCC component of
the recorder displayed during its record to
replay frequency response evaluation.

This performance betters any DAT re¬
corder that I have yet reviewed, and is
undoubtedly an essential feature if Philips
and its supporters are to convince the

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READER INFO NO. 5

ELECTRONICS Australia, October 1992

THE CHALLIS REPORT

purists that even if they are losing some
data (which they can't hear), then they
aren't going to lose any of the data that
they can hear.

I repeated the evaluation using the
digital input with data taken from a
number of our CD test discs, and not
surprisingly I found that the record/replay
performance by means of this input
source was equally good.

Having excited myself with the superb
record-replay response of the DCC900, I
thought that it would be a good time to
determine whether the linearity would
prove to be as good — and also what
the signal to noise ratio would be like.
Well, the linearity proved to be good —
almost as good as some of the best CD
players, but not quite as good as the latest
and best DAT's, nor the professional CD
players and recorders, which obviously
have the edge when playing this critical
numbers game.

The signal to noise ratio also turned out
to be good, with a genuine 94dB(A) per¬
formance. This is truly excellent, when
you consider how much data must have
been excised and modified in the inter¬
vening PASC data encoding process.

It was then that I thought that I should
look at the recorder's abilities when it
comes to replaying conventional analog
compact cassettes. I loaded two reference
replay cassettes, and to my surprise, the
performance was not nearly as good as I
would have liked — nor frankly would I
have expected, when reviewing a piece of
equipment that is going to sell for ap¬
proximately $1400.

The frequency response was modest to
poor, exhibiting a high end response that
was comparable to a cheap compact cas¬
sette recorder in your car, or a cheap
'boom box' which you can pick up for
$200. The thought struck me: is Philips
trying to uplift the new medium in the
public's estimation, by offering a reduced
performance from the old medium? Perish
the thought — Philips wouldn't be so
sneaky! Anyway, if they are, I would sug¬
gest that they reassess this position. This is
not the way to advance the new medium,
by sticking daggers in the back of the old.

I progressed to evaluations of channel
separation, which were excellent but not
superb — although I acknowledge they
are more than good enough for home
recording. I then evaluated the DCC's
record to replay distortion characteristics,
which are superb at the top of the range,
and more than adequate down to - 70dB
(which puts it on a par with the conven¬
tional compact cassette) and rapidly ap¬
proach the same high levels as a
conventional CD player, once you go
below the -70dB point

I was in such a hurry to take the player
home to write this review that I forgot to
check out the wow and flutter figures. For
this I have metaphorically kicked myself
afterwards, but it was too late because I
only had the system for the weekend.

Listening tests

I must admit in the short time that I had
the DCC900 I had a lot of fun, for al¬
though I complained loudly about its
quirks and new features which took some
getting used to, the music that it produced
is exemplary, and the few pre-recorded
tapes provided were good to excellent —
although I suspect poorly selected to dis¬
play the best features of the medium.

I was not fazed by this problem, and
decided to record my own tapes using my
own material so that I could carry out the
type of A-B checks and comparisons
which are essential. Here again I drew on
the resources of my external support
group, who have displayed critical and
objective capabilities which I suspect are
better than my own.

The first tape we recorded was of
soprano Kathleen Battle combined with
trumpeter Wynton Marsalis in Baroque
Duet (Sony Classical SK 46672). This is a
truly outstanding disc, making it more
than suitable for this task.

We carefully A-B'd the disc with the
tape, and I noted with amusement that
nobody in the test group could tell the
difference between the original and the
tape copy — no matter how hard they
tried. Kathleen Battle's beautiful voice
is a particularly good reference source
for comparison, as is Wynton Marsalis'
trumpet, yet there was absolutely no
audible or detectable difference between
the two sources.

I progressed to more conventional
pieces of piano with orchestra, featuring
Yefim Bronfman and Esa-Pekka Slonen
in Rachmaninov's Piano Concertos
No.2 and 3 (Sony Classical SKJ47183).
This particular rendition displays truly
passionate playing, matched by superb
recording techniques.

Once again in A-B testing we just could
not pick the difference between the
original CD version and the DCC tape
copy. In point of fact half of the group
were convinced that the CD was the tape,
and that the tape was the CD — and they
tried very hard.

The last disc that I used for A-B com¬
parisons was a relatively unusual disc
featuring the Robert Hohner Percussion
Ensemble, in a disc entitled Different
Strokes (Digital Music Products DMP CD
485, distributed by PC Audio in Brisbane).
The broad-band music and data con¬
tained on this disc provides extremely dif¬
ficult signal content for any tape recording
medium, and although it may not satisfy

all tastes, is nonetheless as interesting and
novel as it is suitable for comparative test¬
ing speakers or tape recorders.

Again, as hard as we tried, we simply
could not pick the difference between the
original and the tape copy. As a result of
this we firmed up our view that the
DCC900 will be extremely hard to beat

For the heck of it, we then took a
Nakamichi Dragon (which is admittedly
five years old), and repeated the exercise
with two of the three test discs. Although
this was a somewhat unusual approach,
what we found was that if you have a top
of the line analog cassette recorder using
the best metal tapes (which is what we
did), the differences in record to replay
performance between it and a DCC are
neither as wide nor as marked as either
you or we may have expected.

Although we proved that DCC is better,
we still formed the view that there is
still plenty of life and considerable
mileage left in conventional analog
cassette recorders, particularly where the
recorders are in the upper quartile of cur¬
rent technology.

Summary

Based on my brief and somewhat
rushed assessment, I am now convinced
that DCC offers a direct path through
which the average purchaser can
achieve higher home recording fidelity
without necessarily having to dig too
deeply into their pockets. Having pur¬
chased one of the new recorders, he or
she will be able to purchase much better
quality pre-recorded tapes than have been
previously available, and derive a direct
and obvious benefit

Notwithstanding this obvious ad¬
vantage, I suspect that it won't necessarily
be the excellent fidelity and frequency
response of DCC which will determine its
long-term success or failure. This may
well hinge upon ergonomic design fea¬
tures, and in particular the functional
operating time — including the delays in
operating the record mode and searching
for specific tracks.

It's possible that these delays may
alienate users, because the public has
now become used to the convenience
and speed of operation of the ubiquitous
CD. The degree to which we have come
to expect this responsiveness and speed
may well determine whether DCC ul¬
timately gets the 'thumbs up' or the
'thumbs down', in the marketplace.

The Philips DCC900 recorder has a
width of 440mm, a height of 150mm and
a depth of 335mm. It weighs 9kg, and
present indications are that when
released, it will have an RRP of $1400.

Our thanks to Philips Australia for
the opportunity to review the advance
sample machine. ❖

ELECTRONICS Australia, October 1992

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READER INFO NO. 6

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VENUS MAPPING DONE?
MAGELLAN NEARS END I

In May 1989, NASA launched an 'economy' spacecraft which then made its way to our neighbouring
planet Venus. Three months later, Magellan entered Venusian orbit and began methodically scanning the
planet using its synthetic aperture X-band radar. Since then it has sent back an incredible stream of high
resolution images, which have provided scientists with many surprises. But with the planet now almost
fully mapped, budget cuts look like forcing NASA to 'pull the plug' on Magellan next year.

by KATE DOOLAN

1989 was the year that saw the re-emer¬
gence of space science in the United
States, after a decade long hibernation.
The incredible Voyager 2 spacecraft en¬
countered the planet Neptune for the first
time in August In October, Galileo started
its long journey to Jupiter. But earlier,

Magellan had become the first planetary
spacecraft to be launched from the space
shuttle and sent on its way to Venus.

For the last two year then, the Magellan
spacecraft has been mapping Venus and
providing scientists with a most thorough
picture of the planet which was always

thought to be Earth's twin. It has been
found that Venus is not the sedate planet
that it was supposed to be, but a planet
with a violent geological history.

Venus is located 108 million kilometres
from the Sun and 48 million kilometres
from Earth. Named after the Roman god-

ELECTRONICS Australia, October 1992

dess of love and beauty, Venus is covered
by thick, swirling clouds made up of
sulfuric acid droplets. The atmosphere
is comprised of carbon dioxide with
traces of water vapour.

The planet's surface has continent-sized
plateaus, deep canyons and mountains
thought to be as high as Mount Everest
The surface has a temperature of 470°C,
which is sufficient to melt lead. It could be
said that Venus is the ultimate women's
world, as nearly all the features of the
planet are names after women of history
and mythology.

The only exception is Montes Maxwell
— a mountain named after James Clerk
Maxwell, a scientist who did much of the
early work on Venusian geology. Unusual¬
ly, a day on Venus is 243.0 Earth days
long which is longer than the planet's year
of 224.7 Earth days.

Because of Venus' close proximity to
Earth, both the United States and former
Soviet Union have been sending
spacecraft to the planet for the last
31 years. The most recent spacecraft to
travel to Venus before Magellan were the
Soviet's Venera 15 and 16 which radar
mapped Venus during 1983. During the
following year, the Soviets again sent two
balloons and landers which sent back data
on previously known surface features.

It was in the mid seventies that scientists
at the Jet Propulsion Laboratory (JPL) in
Pasadena California, decided to design a
Voyager-type spacecraft to explore Venus
in the same detail that Voyager had
studied the outer planets.

However, gone were the days in which
the National Aeronautics and Space Ad¬
ministration (NASA) received large
budgets for planetary science. In the early
eighties, there were dangers that the
planetary science programs would be
wiped out altogether.

In response to this danger, the JPL scien¬
tists decided to redesign their planned
spacecraft to make it the Venus Orbiting
Imaging Radar, with only one scientific in¬
strument — a synthetic aperture radar. But
political problems were threatening even
the lower cost projecL

Congressional funding for the Venus Or¬
biting Imaging Radar was approved in mid
1984 and the program started later that
year. There was a cost to this: the
American efforts for the return of Halley's
Comet in 1985/86 were cancelled and the
only scientific activity planned was a
space shuttle flight that never flew.

Shortly after the start of construction the
VOIR was rechristened Magellan after the
famous Portugese explorer Ferdinand
Magellan (1480 - 1521) who became the
first man to circumnavigate the world.

Magellan was scheduled to be launched
in 1987 from the space shuttle, but the
Challenger accident delayed launch until

1989. The accident also caused a
redesign of Magellan's journey to Venus,
as the liquid fuelled Centaur Upper
Stage that was to be used was cancelled
as a result of post-Challenger investiga¬
tions. So JPL designers had to adapt the
spacecraft to the solid fuelled (and safer)
Inertial Upper Stage.

Economy model

Magellan is not your average planetary
spacecraft, as it was constructed from
spare parts from other planetary spacecraft
such as Mariner, Galileo , Viking and
Voyager to save money.

Magellan is 6.4 metres high and weighs
3460 kilograms. Electrical power for the
spacecraft is provided by two solar panels
measuring 12.6 metres in diameter.

The solar panels supply 1200 watts of
power to Magellan during its mapping
phases. The panels have a single degree of
freedom about the solar array axis, to
allow tracking of the Sun despite the
changing position of the spacecraft during
its flight Voltage regulation to the
spacecraft is tightly controlled by a shunt
regulator unit, which diverts excess
power from the solar panels to maintain
voltage at proper levels.

Both direct and alternating current are
provided, with DC power at 24 to 33
volts, and 2.4 kilohertz AC power at 50
volts. Two 26.5Ah 22-cell nickel cadmium
batteries provide power to Magellan
when it is in the shadow of the planet
This allows normal spacecraft operations
independent of solar illumination.

The attitude of the Magellan spacecraft
in relation to the planet is controlled by
three reaction (momentum) wheels

driven by electric motors. Their motion
stabilises the spacecraft and maintains its
properattitude.

During Magellan's journey to Venus, it
was pointed in the proper direction with
the help of gyroscopes which were con¬
tinuously updated using stars as reference
guides.

Twenty four multipurpose liquid propel¬
lant hydrazine thrusters provide several
functions — spacecraft attitude control,
trajectory and orbit correction and reac¬
tion wheel decelerations.

Positioned in the middle of the ten sided
equipment bus is a single propellant tank,
which at launch contained 132.5
kilograms of monopropellant hydrazine.

A helium tank is attached to the struts of
the propulsion module structure and can
be used, if necessary, to offset drops in the
pressure of the hydrazine system. The
STAR 48 solid rocket motor was used for
orbital insertion at Venus.

At launch it weighed 2146 kilograms
of which 2104 kilograms were propel-
lanL The motor's 30,000 kilograms of
thrust reduced the speed of transfer from
interplanetary trajectory into orbit
around Venus.

Control systems

Commands transmitted from Earth to
Magellan are received by the radio fre¬
quency subsystem and are relayed to the
command and data subsystems (CDS),
where they are interpreted and acted
upon. This system also controls the ac¬
quisition and storage of engineering and
science data and sends that information
back to Earth.

The CDS stores command sequences for

Prior to departure, in KSC’s Vertical Processing Facility, STS-30 Mission
Specialist Mary Cleave performs a sharp-edge inspection of the spacecraft
‘iMagellan

ELECTRONICS Australia, October 1992

Venus mapped

The eastern edge of Alpha Regio is shown here. Seven circular , dome-like hills,
averaging 25km In diameter with maximum heights of 750 metres, dominate the
scene, and are thought to be very thick lava flows on relatively level ground.

up to eight days of radar operation of the
mapping phases. There is also a provision
for receiving and immediately executing
separate commands issued from the
ground.

Engineering data is normally transmitted
to Earth over a real time S-band link,
which has transmitting power of five
watts. When a real time link is not pos¬
sible, the data is tape recorded and
played back by way of the X-band
high-rate link which has transmitting
power of 20 watts. (S-band is 2 - 4GHz,
X-band is 8 - 12GHz).

Magellan's brains are comprised of two
ATAC 16 computers, which are located in
the attitude control subsystem, and four
1802 microprocessors in the Command
and Data Subsystem. All the computers
are in a duplication configuration as in¬
surance against breakdowns. The com¬
puters are fully reprogrammable and are
modified equipment from the Galileo
spacecraft.

The radar scanning data is stored on
two multitrack digital tape recorders, for
later playback over the high rate X-band
link. There is no provision for real time
transmission of radar data, because the
large antenna must be pointed at Venus
whilst mapping.

Data storage capacity of the tape re¬
corders is about 1.8 billion bits each. The
tape recorders are used primarily for the
recording of radar data, but as noted ear¬
lier, low rate engineering data can also be
stored during mapping or at other times
when engineering data cannot be trans¬
mitted back to Earth in real time.

Radio links

Magellan Telecommunications Subsys¬
tem (TCS) contains all of the hardware re¬
quired to maintain communications with
Earth. The subsystem contains the radio
frequency subsystem and the low-gain,
medium-gain and high-gain antennae.

Magellan is capable of receiving X-band
or S-band uplink signals whilst transmit¬
ting data downlinks via X-band or S-band
simultaneously. The uplink data rates are
7.8125 or 62.5 bits per second. From
Venusian orbit, engineering data is sent to
Earth at 1.2 kilobits per second through
the high-gain antenna via S-band while
simultaneously transmitting the recorded
radar data at 268.8 kilobits per second.
Backup data rates of 40 bits per second
for engineering telemetry and 115.2
kilobits per second for radar data are
available for emergencies.

The radio frequency subsystem is an as¬
sembly of separate units joined together
by RF, control, power and telemetry ca¬
bling. It is joined to the S-band antenna by
semi-rigid coaxial cables and the X-band
high-gain antenna feed by two waveguide

runs. The high-gain antenna is constructed
of lightweight graphite epoxy sheets
mounted to an aluminium honeycomb for
rigidity. The medium-gain antenna is a
conical horn 460mm in diameter and
610mm long. The low-gain antenna is a
cylinder 380mm long and 100mm in
diameter.

To communicate with Earth, Magellan
uses the facilities of the NASA Deep Space
Network (DSN). With stations located in
California, Spain and Australia, the
spacecraft has been able to communicate

with ground controllers every minute of its
mission. The NASA Tracking and Data
Relay System is also used as a backup for
the Deep Space Network.

With a conventional radar, the resolu¬
tion of an image depends on antenna size
— the bigger the antenna, the better the
resolution. However, having a large anten¬
na on Magellan would be too expensive
and too difficult to manipulate. To solve
this dilemma, the signals from Magellan's
Synthetic Aperture Radar (SAR) are com¬
puter processed on Earth so that they im-

This image Is the crater Cleopatra, located on the eastern slopes of Maxwell
Montes, the highest mountain range on Venus. Cleopatra measures about 100km
across and 2.5km deep. From the data available, scientists have been unable to
determine If Cleopatra was a meteorite impact crater or a volcanic depression.

ELECTRONICS Australia, October 1992

The complex pattern of intersecting ridges and valleys called ' tessera ' indicate
that this portion of Alpha Regio in the Lavinia region has undergone many
episodes of horizontal motion. The tessera covers an area of about 125km.

itate the behavious of a, large antenna on
the spacecraft By using this synthesis
process, the onboard radar sensor operates
as if it has a large antenna and it
produces high resolution images even
though Magellan has a small antenna.
This computerised process of 'aperture
synthesis' is what gives the SAR its
resolving power as well as its name.

As Magellan passes over the Venusian
surface, its dish antenna looks
downward and to the left side of the
spacecraft's orbit path. For 37 minutes,
the SAR antenna emits several thousand
radar pulses each second. Travelling at the
speed of light, the pulses strike and il¬
luminate a 25 kilometre wide swath of the
planet's surface, and then immediately
bounce back and are received by the
spacecraft

By recording the returned pulses, two
measurements on each pulse allow loca¬
tion of each point on the planet's surface.
The first measures the time it takes for the
radar signal to return to Magellan, giving
the spacecraft's distance to that point The
second measures the returned signals for
their Doppler effect — a shift in frequency
caused by the spacecraft's motion over the
surface. This second measurement gives
the location of the point with reference to
the spacecraft's line of flight, since Magel¬
lan is either approaching or receding from
the point

Shown here are three large meteorite impact craters from the Lavinia region.
Found in an area of fractured plains, the craters show many features typical of
meteorite impact craters , including rough (bright) material around the rim,
terraced inner walls and central peaks.

Construction costs

The Magellan spacecraft itself was built
by Martin Marietta Corporation while its
Synthetic Aperture Radar was constructed
by the Hughes Aircraft Company. The
Magellan probe is managed by the Jet
Propulsion Laboratory and the Tracking
and Data Relay System is managed by the
Goddard Space Flight Centre. The delay
caused by the Challenger explosion
resulted in Magellan's costs going up by
US$200 million, to a total mission cost of
US$500 million. Another US$90,000 was
added to the mission cost in October
1988.

Whilst undergoing final preparations to
launch, a technician at the Kennedy Space
Centre, incorrectly connected the
spacecraft to a test battery and caused
an electrical fire. Fortunately the
spacecraft was not seriously damaged
and the launch preparations continued
on schedule.

Magellan was launched into space on
the STS30 space shuttle mission, the fourth
shuttle mission after the commencement
of shuttle flights after Challenger. The mis¬
sion commanded by Dave Walker, pilot
Ron Grabe and Mission Specialists Mary
Cleave, Mark Lee, and Norm Thagard had
a launch window of only 25 days. If
Magellan missed that launch, it would
have had to wait another two years for

ELECTRONICS Australia, October 1992

Venus mapped

This image was taken from the eastern flanks of Freyja Montes In Ishtar Terra ,
and is dominated by a highly fractured dome measuring approx. 70 x 125km. The
‘turtieback’ appearance is the result of two sets of intersecting fractures.

launch. Fortunately, the shuttle Atlantis
was delayed for only one day and was
launched from the Kennedy Space Centre
in Florida on May 4, 1989.

Once in Earth orbit, Magellan was
launched from the payload bay and then it
was propelled into a Venus trajectory by
the Inertial Upper Stage (IUS). Once
Magellan was outside the Earth's gravita¬
tional influence, it had a relatively un¬
eventful cruise to Venus and was inserted
into orbit around the planet on August 10
1990.

Arriving at Venus, however, Magellan
caused the ground controllers at JPL noth¬
ing but trouble. On the day it arrived in
Venusian orbit, the spacecraft's com¬
munications system stopped working.

Soon after, the system started working
and then failed again. To ensure that
Magellan would keep working, ground
controllers tracked down the problem
which was attributed to a faulty com¬

puter chip. After a 20 day checkout,
Magellan began mapping Venus and the
surprises started.

Many surprises

The radar images sent back have been
the most detailed images ever seen of
Venus. The terrain of the planet was
revealed to have a tortured topography,
with fault like cracks in regular patterns.
Craters as large as the combined areas of
Melbourne and Sydney were discovered
as were congealed rivers of lava measur¬
ing up to 320km long. Earthquakes or
more correctly 'Venusquakes' were also
detected.

Magellan completed its first mapping
cycle in May 1991 and in that time
mapped 84% of the planet. It then
started its second mapping cycle. Using
images from both the first and second
cycles, scientists began to use the stereo
imaging to make comparisons of the

Venusian surface. In August 1991, scien¬
tists comparing two images found the
largest canyon in the Solar System. The
canyon, 6000 kilometres long and 1.8
kilometres wide, is longer than the River
Nile. But unlike the Nile, the canyon is a
single channel lacking tributaries and is
the same width for its entire length.
Another discovery at the same time was a
crumbling cliff, which had been caused
byVenusquakes.

The biggest shock came in November
1991. Scientists studying images of the
planet's second tallest mountain 'Maat
Mons' discovered that the mountain was
recently covered by lava.

Rocks that sit on top of most Venusian
mountains appear to weather quickly in
the hot atmosphere, which creates soil
that is rich in iron sulfide. This mineral
shows up easily on radar. If the Maat
Mons peak does not show traces of iron
sulfide, it means that it has been covered
by lava in only the last couple of years.

Resurfacing on the Venusian lowlands
by lava flows appears to take place on a
regular basis, as the lowlands are free of
craters. This is said to be caused by peri¬
odic lava flows. Magellan has found
evidence of these lava flows, which in¬
clude domelike upwellings and hardened
streams of rock trailing down the sides of
the planet's mountains.

As yet, Magellan has not found any vol¬
canoes erupting, but scientists have ample
evidence to suggest that Venus is the
fourth body in the Solar System to have an
active volcano system — after Earth,
Jupiter's moon lo and Neptune's moon
Triton.

End in sight

As exciting and successful as the
Magellan mission has been for NASA, it is
not being allowed to continue. Recent
budget cuts by NASA Headquarters have
ordered that the Magellan be cancelled in
1993.

Another prominent solar system mission
casualty is that of the Comet Rendezvous
Asteroid Flyby (CRAF), which has been
cancelled completely. The budget cuts
have been attributed to the much-
maligned Space Station Freedom project,
beginning to take priority at NASA in both
time and money.

As of January 1992, Magellan had
mapped 95% of the Venusian surface. By
the time of its cancellation, it will have
mapped all of the planet— adding greatly
to our knowledge of the planet that until
recently was thought to be Earth's twin.
Not a bad achievement, for a leftover
spacecraft

The author would like to thank Mary
Hardin and Dr Craig Waff, of the Jet
Propulsion Laboratory, for their assistance
in the completion of this article. ❖

ELECTRONICS Australia, October 1992

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See the review in Electronics
Australia March 92 -

“Electronics Workbench is
certainly the easiest simulator
I've ever used''

Peter Philips

Electronic

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The Electronics Lab you keep
in your PC!

YES you can now build,
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It’s so easy with Electronics
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Editing circuits is easy as wires
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It’s much faster than building
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the result of 10 years innovation
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Analog Module includes

• Comprehensive parts bin
includes op-amps, zeners,
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• Function Generator with sine,
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• Oscilloscope with dual trace,
int/ext trigger, nanosecond
timebase upto 999MHz

• Bode Plotter for frequency
responses and phase shift
(-200 to +200dB)

• SPICE Simulation plus transient
and steady-state simulation

Digital Module includes

• Comprehensive parts bin with
gates, flip-flops, half adders,
displays etc

• Word Generator up to 16x8-bits

• Logic Analyser with 8 channels,
inf/ext trigger

• Logic Converter converts
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boolean

Professional version has
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$429.00

Personal Plus Version is

monochrome. Requires PC/XT/
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APPA 35 CLAMP METER

• 4000 count display

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Ohms to 40ku and continuity
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• Built-in belt clip

$142.80 $119.00 ex tax

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This month we have two bulk buy bargains for you -

400V, 35A Bridges

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Branded, but sorry we aren’t allowed to tell you the name!

25 pin D Conectors

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Kikusui SCOPES

60MHz 3 Channel Scope

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COS5060B $1860.00

40MHz 2 Channel Scope

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COS5041 $1373.00

20MHz 2 Channel Scope

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COS5020 $916.00

Handy Probe
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Artec Tools
Drill ‘N Drive

Rechargeable two speed drill and
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Supplied with
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AC adaptor

3 dril bits-2.0, 3.0, 4.0mm
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A really handy tool for just $69.95

Hot Air Gun

Features

Dual 400/600°C temperature
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1600W output
Built-in safety handle
Hanging hooK for storage
12 month warranty

Many uses for $59.95

SerialTest

PC-based Protocol
Analyser & Data
Line Monitor

The new version of Serialtest
turns ANY PC into a full-featured
serial data protocol analyzer —
even laptop and notebook
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new Com Probe plugs in to your
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The Serialtest package includes
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Serialtest Async is similar to
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sine, pulse, TTL level square

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Frequency Counter

• 1Hz to 100MHz

• 15mV sensitivity to 60MHz

Digital Multimeter

• 3 1/2 digit LCD

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Power Supply

• 0 to 50V, 0.5A

• 15V 1A and 5V 2A fixed

$898.10 inc tax $774.20 ex tax^y

Save on Ultrasonic Cleaner

The latest high-tech way to clean
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8.30am to 5.00pm Mon to Fri. 8.00am to 12 noon Saturday.
Mail Orders add $5.00 min to cover postal charges.

Next day delivery in Sydney add $8.00.

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Live breakout box includes
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READER INFO NO. 7 (inc in N S W)

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CONDITIONS OF ENTRY: 1. The competition is only
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When / Think Batk...

by Neville Williams

Fred Thom and Tasma - 2:

From wires and relays to wireless

After gaining experience in radio receiver manufacture at L.P.R. Bean/Stromberg-Carlson, Fred
Thom and John Smith left in 1929 to form their own manufacturing company. This flourished for
many years, with their brand name ‘Tasma’ becoming widely known all over Australia. But in the
1950’s they began to strike trouble, as did many other local manufacturers.

In 1927, the name L.P.R. Bean & Co
disappeared — to be replaced with
Stromberg-Carlson Australia, still
headed up by Mr L.P.R. Bean. And that’s
how, as a raw recruit to the industry in
the early 1930’s, I myself first heard of
Mr Bean — from itinerant wirers in
local radio factories. In anecdotal terms,
that (adjectival) ‘so-and-so from
Strommys’ was the personification of
everything they resented in the system!

Reading through the draft of these ar¬
ticles, Fred Thom queried the above ob¬
servation as an exaggeration. He had
worked as Bean’s foreman in the early
days, he said, and would have known if
he had been unduly provocative.

He did concede, however, that Bean
had once ruled that process workers
visiting the toilets between normal
breaks had to ‘clock-off’ while so oc¬
cupied! This was in addition to whole

production lines being made to clock
off, if production was held up by a tem¬
porary shortage of components.

Fred Thom says that, from about
1927, the Bean/Stromberg organisation
scaled down its involvement in
telephone equipment and moved into the
importation and manufacture of radio
receivers, with the US company having
become part owners of the Australian
operation.

Fig.4: Caricatures of Fred Thom (left) and his partner John Smith , as published in our predecessor , Wireless Weekly
in late 1934. The cartoonist went by the nom-de-plume 'Hotpoint

ELECTRONICS Australia, October 1992

As an employee, and observing what
was involved, Fred Thom began to
think: “If I can build receivers for
Strommys, I can do the same for
myself! ”

So in 1929, he and two other Strom-
berg-Carlson employees, John E. Smith
and George Woodward, resigned to form
a new company to manufacture domes¬
tic radio sets. Thom and Smith were to
be co-founders, with Woodward, a tool-
maker, becoming their first employee.

As electrical/mechanical trainees,
none had any formal qualifications in
radio. Their total cash reserve amounted
to a meagre £500 ($1000) plus a £1000
loan. But nevertheless they did very
well. As it turned out. Woodward sub¬
sequently went his own way and formed
G.W. Engineering — leaving Thom &
Smith Pty Ltd to gain wide industry
recognition as the manufacturers of
‘Tasma’ brand equipment.

Fred Thom was accepted in 1932 as a
foundation member of the IRE Aust (In¬
stitution of Radio Engineers), over the
signatures of E.T. Fisk (President) and
N.S. Gilmour (Secretary), being made a
Fellow in 1940. He was also awarded
life membership of the IEEE (USA).

Thom & Smith was well placed to
take advantage of the ‘golden age of
radio’ — the 1930’s — and Tasma

About the size of it!

The finishing touches were being
added to Fred Thom’s new factory, sited
directly opposite the existing Thom &
Smith factory.

Signwriter: “You want 'Thom
Electronics Pty Ltd’ painted across the
front of the building?”

Fred Thom: "That’s right.”

Signwriter: "How big do you want the
letters?”

Fred Thom: "How big are the ones
across the road?"

Signwriter: "I wouldn’t know.”

A few minutes later, passers-by might
have noticed Fred Thom and the
signwriter carrying an extension ladder
across busy Botany Road. Fred
steadied it against the T&S factory wall,
while the signwriter ran his rule over the
sign.

Signwriter: "The letters are so many
inches tall.”

Fred Thom: "Then make ours bigger
than that!"

receivers took their place alongside
other major brands on the Australian
radio scene. By 1938, the firm had
around 600 active dealers Australia¬
wide.

Fig.4 shows the circuit of a table
model Tasma autodyne 445kHz super-
het, which conforms closely to the
trends detailed in the ‘Think Back*
column for November 1991.

In conversation, Fred Thom told me
that in its formative period, Tasma used
consignment selling to good effect. They
would consign modestly priced
receivers to selected prospects, e.g.
schoolteachers, with an invitation to try
them out in their own environment. If
unwanted, they could be returned
without obligation. If the recipients
wished to keep them, payment could be
arranged.

“At a time when new receivers were
in strong demand”, said Fred, “few if
any were returned”.

Tasma subsequently diversified into
the production of car radio receivers —
again with encouraging consignment
sales, and an even more encouraging
bulk order from Ford. The latter sets
were branded ‘Tasma-Ford’ in a suitable
script

This, in turn, ultimately paved the way
for T&S to get involved in two-way
mobile communication systems. It was a
courageous step, because the production
of automotive equipment using valves
and vibrator-type power supplies was
never an easy way to ‘make a quid’!

‘Buy Australian’

Fred recalls that, around 1934, the
Chief Engineer of the Australian Post
Office decided that the letting of con-

Tasma A.C. Broadcast Mantel Model 180

57 58 57 58

Flg.5: Circuit details of the Tasma model 180 receiver, an early mantel model released in 1933. Reproduced from the
HRSA Newsletter for January 1991, the numbered circles relate to points which restorers may need to check.

ELECTRONICS Australia, October 1992

WHEN I THINK BACK

tracts for telecommunication com¬
ponents had become a ritualistic alloca¬
tion to major suppliers like STC and
GEC.

On the assumption that key items like
the 3000-type relay could not be mass
produced in Australia, these firms had
allegedly been submitting non-competi¬
tive quotes for the imported product.
This, said the Chief Engineer, was a
nonsense!

Accordingly, he approached Thom &
Smith and said that if they would tool up
for local production — at their own risk
— using Australian raw materials, he
would place an initial order for 10,000
units and do his best to support future
expansion.

Despite their preoccupation with
radio, T&S decided to ‘give it a go’.

They found a local supplier of nickel-
silver for the springs, while enamelled
wire had become available from Rola.
After a hassle about quantities, BHP
came up with suitably annealed iron for
the cores and, much to the surprise of
STC, AWA and others, Tasma achieved
the ‘impossible’: an all-Australian 3000
type relay.

Locally made telephone dials were
also said to be out of the question, but
another Australian company came up
with them. In the end, the APO’s ‘made
in Australia’ initiative was rewarded
with hundreds of thousands of pounds
worth of local production, with some¬
thing like 60 permanent employees in¬
volved in Tasma alone.

Price-competitive, and with the ad¬
vantage of being Australian-made, Fred
says that Tasma became one of the firms
which finally forced companies like
STC and AWA to commit themselves to
local production of telecommunications
equipment, including complete automat¬
ic handset telephones.

This diversification carried over into
the wartime years, with Thom & Smith
for one, becoming deeply involved in
radio and radar equipment for the armed
forces. T&S made transmitters by the
hundreds, ranging from 150W to 500W,
both AM and FM and from 150kHz to
150MHz.

To emphasise the point, Fred and his
son Ian showed me a carton full of in¬
struction manuals, for all manner of
free-standing and rack mounted profes¬
sional equipment — a world apart from
telephones and domestic receivers.

In a profile of Fred Thom and Tasma,
Rydges magazine for March 1, 1952 ac¬
cords a share of the credit for Tasma

technology to their Chief Engineer, Eric
Fanker.

It also adds that, in addition to major
items like the above, Tasma mass
produced smaller items — such as
100,000 relays and 100,000,000 plastic
bullet tip cores for .303 ammunition.

“We made all manner of things” says
Fred. “You name it, we made it and it
performed well in the field!”

Post-war problems

With the cessation of hostilities,
military orders lapsed overnight and it
was back to civilian telephones — with
a huge back-log of new service require¬
ments worldwide, which swamped the
resources of overseas manufacturers. If
Australians wanted new phone services,
Australian firms like Tasma had to pro¬
vide the equipment — as well as coping
with a huge demand for new post-war
radio receivers.

This was followed by the Korean war,
and already stretched companies were
faced with renewed calls for military
equipment — to be supplied on a cost-
plus 5% basis, with the Government
keeping tight rein on the total. In that
environment, it proved difficult, if not
impossible, to cover overheads.

“Being intensely Australian”, accord¬
ing to Fred Thom, “and from a sense of
duty”, his company went along with the
arrangement, diverting a large propor¬
tion of their resources for a totally inade¬
quate return — and in the process,
compromising normal commercial
production and profit!

Fred says that he tried in vain to
reason with the bureaucrats, but, aware
that they were “on a good thing, they
wouldn’t come to the party”.

With a staffing level of around 800,
Thom & Smith were suffering ‘appalling
losses’. The position was exacerbated by

Fig.6: The NSW police dog 'Zoe' fitted with a portable radio prominently
marked ‘Tasma’. At the time, the Idea appeared to have potential for difficult
rescue situations.

ELECTRONICS Australia, October 1992

Fig.7: Produced by Thom & Smith, the AT-15A was used principally by the
RAAF. Operating in the frequency range 150 - 500kHz, the 350/500W trans¬
mitter was used mainly for homing and airport control .

an exasperating strike, and around
1952/3 the company was faced with a
severe liquidity crisis. This was with
television looming, and there was no
overseas affiliate to which they could
turn for support.

Thom & Smith’s answer was to merge
with President Consolidated, a high
profile refrigerator manufacturer. The
merger was by an exchange of shares,
with Thom & Smith becoming a sub¬
sidiary company but retaining its public
identity.

The crisis appeared to be under con¬
trol, especially when Fred Thom
managed to negotiate a licence in the
USA to re-design, manufacture and
market in Australia TV receivers
branded ‘Motorola’.

But the ink on the licence had scarcely
dried when President Consolidated en¬
countered a liquidity problem of its own.
Assured that everything was under con¬
trol, Fred Thom carried right on with the
repositioning of his old company for
‘Motorola’ TV production, drawing
what assurance he could from the
Motorola licence in his pocket and the
parcel of President shares that he had
accepted in lieu of cash for their part-
ownership.

Eventually, however, President folded

completely — exposing Thom & Smith
as a key viable asset.

At that point, Fred might conceivably
have bought back his old company. But,
as he says, he had insufficient real
‘brass’ — just a parcel of relatively
worthless President shares which, with
hindsight, he should have unloaded
while they were still saleable.

So he had to negotiate the enforced
sale of his entire one-time business to
the Pope group. Unwisely (“I was a silly
bugger”) he agreed to the transfer to
Pope of the Motorola licence which,
with hindsight, he should have re¬
negotiated for himself. That rendered
him redundant, and just over a year later.
Pope terminated his services as manager
(“I was out on my ear! ”).

Pope replaced Fred Thom with
another old-timer, Bert Israel. But I
gather from the TSA monograph that it
wasn’t a very rewarding relationship —
with Pope, in turn, being taken over by
the Simpson group.

Rather than retain Thom & Smith as a
going concern, however, Simpsons ter¬
minated TV set production, selling up
the premises, the tooling and everything.

The historic telecommunications 3000
relay equipment was purchased by the
Spastic Centre and it, along with Bert

Israel and a hand-picked group of
employees, became an essential com¬
ponent of that organisation’s Centre In¬
dustries.

Fred Thom, meanwhile, with a few
thousand dollars capital salvaged from
the debacle, had built a smaller factory
across the road from the original Tasma
premises in Botany Rd, Mascot.

There he founded a new company,
Thom Electronics, taking on board con¬
tracts which he could handle with other
employees from the original Tasma staff,
and without the specialised tooling that
had gone to Centre Industries.

Some time later, and by agreement,
James N. Kirby bought into Thom
Electronics, retaining Fred Thom as
manager.

This time around, however, Fred sold
a part-interest in the business but
retained title to the premises, so that he
also became the landlord. Between
them, Kirby held rights to the Crosley
label, Fred knew how to build TV
receivers from the Motorola days, and
the Crosley TV range duly appeared on
the Australian market.

Realising, as landlord, that the
enterprise was outgrowing the existing
premises, Fred Thom privately sought
and found a much larger factory in the
suburbs. After “squeezing the banks and
God knows what”, he secured a pur¬
chase option on it and offered to lease it
to Kirbys at the existing ‘per foot’ rate,
which they accepted.

So it was, as Fred says, that he “over¬
saw the production of thousands of
television sets” — many of them on his
own premises — but always for some¬
body else. “There were all sorts of
Tasma products, but never a Tasma
TV”.

But as the wheel of circumstance
turned, General Electric bought first one
third, then another third of Kirbys. “And
so help me,” says Fred Thom, “GE
made a mess of it, too. The refrigerators
went to Rank and the rest is just a
memory”.

He concludes: “Fortunately, as
General Electric, they still had to rent
the factory from me — and that fed me
until the operation folded!”

Nowadays other lessees are support¬
ing the TTiom family, but the Tasma
brandname has passed into history.

Such then is the bewildering Thom &
Smith/Tasma/Thom Electronics story, as
told by Fred Thom himself. Some may
see it as an industrial ‘whodunnit’; to
others it will be but a sad reminder
of a fate which befell a whole array of
once prosperous Australian electronics
manufacturers. *

ELECTRONICS Australia, October 1992

NEW BOOKS

Vintage radio

OLD TIME RADIOS! RESTORA¬
TION AND REPAIR, by Joseph J.
Carr. Published by Tab Books, 1991.
Soft cover, 235 x 188mm, 256 pages.
ISBN 0-8306-3342-1. Price $36.95 plus
postage.

Now that collecting old radios and
other equipment of the valve era has be¬
come quite a flourishing hobby, there’s a
growing need for information on how
valve-based circuits work and the most
efficient troubleshooting and repair tech¬
niques to use with them. (What a pity
that many of us threw out our old data
books and manuals!)

This book by well-known US techni¬
cal author, columnist and radio amateur
Joseph Carr is designed to provide a
good basic introduction to radio receiver
operation, the operation of valves, the
various kinds of valve radios and then
the practicalities of repairing and restor¬
ing valve radios. And it seems to do this
extremely well, to my mind. The mate¬
rial is logically ordered, the coverage is
quite thorough and the text is written in
Mr Carr’s usual easy to read style. And
although it’s written mainly for the US
market, most of the content is equally
applicable here.

In short, a book that should be of great
interest and value to anyone involved in
repairing and restoring old radios — es¬
pecially those just starting out.

The review copy came from Arthur
Courtney of Resurrection Radio, 51
Chapel Street (PO Box 1116), Windsor
3181. (J.R.)

Micro-based systems

MICROPROCESSOR SYSTEM DE¬
SIGN, by Michael Spinks. Published
by Butterworth-Heinemann (Newnes),
1992. Soft cover, 245 x 190mm, 247
pages. ISBN 0-7506-0279-1. Recom¬
mended retail price $69.95.

This book is an introduction to the
concepts and techniques which go into
the design of electronic circuits, espe¬
cially those based on microprocessors. It
takes a practical approach and concen¬
trates on a few relatively simple tech¬
niques, which can be combined to build

up complex circuits. Almost all the cir¬
cuits and ideas presented have been used
in real industrial situations.

The basic building blocks of electronic
systems are covered in chapters 1-2, on
digital logic and analog components.
The book then covers the more advanced
topics of op-amps and programmable
array logic (PALs). Microprocessors and
the bus-based system are dealt with in
chapters 5-6, while the final two chapters
give miscellaneous circuits plus practical
techniques like prototyping, debugging
and PCB layout.

The book is very easy to read, and well
laid out and illustrated. It also claims that
‘no previous knowledge of electronics is
assumed’, and the meaning of all termi¬
nology is fully explained. However be¬
cause the amount of material covered is
quite extensive, I suspect that someone

truly without any ‘previous knowledge’
would find it hard going.

However, for the new engineer, techni¬
cian or electronics student who wants to
understand how ‘real-life’ circuits are
developed, or who wishes to revise or
extend their knowledge in this area of
microprocessor system design, then the
book should be very useful.

The review copy came from
Butterworths, 271-273 Lane Cove Road,
North Ryde 2113. It is available from
technical bookshops. (P.M.)

Primer for C++

THE WAITE GROUP’S C++
PRIMER PLUS, by Stephen Prata.
Published by Waite Group Press,
1991. Soft covers, 228 x 178mm, 720
pages. ISBN 1-878739-02-6. Recom¬
mended retail price $55.00.

With object-orientated programming
or ‘OOP’ very much the current vogue,
this introductory book on the ‘generic’
C++ OOP language should be of consid¬
erable interest It has been very well re¬
ceived in the US, winning author Dr
Stephen Prata the Computer Press
Association’s 1990 Best How-To Com¬
puter Book Award. Prata is a teacher of
astronomy, physics and computer sci¬
ence at the College of Marin, in
Kentfield, California, and has also writ¬
ten popular books on UNIX, QuickC,
QuickBASIC and standard C.

As the name suggests, he has written
this further book to provide a sound,
practical yet easy-to-follow introduction
to C++, for those with some background
in programming but not necessarily in C.
This makes it a bit different from many
others, which assume you’re already
quite proficient in C.

From my quick inspection, it seems to
be well planned, clearly presented and
quite accessible — features we’ve come
to expect from both Dr Prata and other
Waite Group authors. So if you’re in the
market for a C++ primer, this one cer¬
tainly belongs on your short list.

The review copy came from distribu¬
tor Woodslane, of 8/101 Darley Street,
Mona Vale 2103, but copies should be
available at all major and technical book¬
stores. (J.R.) ❖

ELECTRONICS Australia, October 1992

MICROWAVE

REPAIR AND MAINTENANCE

TROUBLESHOOTING AND REPAIRING SOLID
STATE TVs, 2nd edition

Davidson 0.8306.3893.8 RRP$41.95
Homer Davidson ran his own radio and TV repair
business for 38 years. Packed with examples, photos
and diagrams for every kind of TV circuit, this book
helps you pin-point and fix virtually any malfunction
quickly and easily. Covers HDTV, stereo sound circuitry,
modular chassis and large screen models. 605 pages.

TV REPAIRS FOR BEGINNERS, 4th edition

Zwick 0.8306.2180.6 RRP $37.95
Completely updated and illustrated with schematics and
photos, this book makes it easy to find and correct a
huge variety of problems on all types of set. It even
guides you on which repairs you can safely do yourself
and which need professional help. 354 pages.

TROUBLESHOOTING AND REPAIRING VCRs,

2nd edition

McComb 0.8306.3777.X RRP $34.95
McComb explains to the technician how to carry out
routine maintenance, and supplies flowcharts for
faultfinding and repair. He even covers problems not
caused by the VCR, like anti-copying signals! 412
pages.

HOME VCR REPAIR ILLUSTRATED

Wilkins 0.8306.3711.7 RRP $37.95
Most VCR problems are caused by one component that
is worn, loose, bent or dirty. Save money by doing the
repair yourself—you don’t need expensive tools or test
equipment! Detailed photos illustrate how to find and
correct most common VCR problems. 383 pages.

TROUBLESHOOTING AND REPAIRING
CAMCORDERS

Davidson 0.8306.3337.5 RRP $42.95
Gain a profitable new skill fixing home video cameras!
This book contains all you need to know about cassette
problems, automatic iris, white balance and focus, servo

TAB/McGraw-Hill

liniM NEW & BESTSELLING BOOKS

circuits, motors, audio circuits and mikes—and much
more! 533 pages.

LENK S VIDEO HANDBOOK: Operation and
Troubleshooting

Lenk 0.8306.4072.X RRP $44.95
The all-in-one guide to consumer video! Includes
chapters on colour and b/w monitors, Beta and VHS
VCRs, cameras, camcorders and 8mm video, featuring
operating procedures, circuit theory, sample test and
adjustment procedures, simplified circuit diagrams and a
logical troubleshooting approach. 384 pages.

TROUBLESHOOTING AND REPAIRING COMPACT
DISC PLAYERS

Davidson 0.8306.3107.0 RRP $32.95
All the latest technology used in component, portable
and in-car units is here. The manufacturers provided the
literature and schematics used in this book, so you’ll be
able to repair servo control loops, remote control
systems, optical lenses and laser assemblies, and the
rest! 338 pages.

MICROWAVE OVEN REPAIR, 2nd edition

Davidson 0.8306.3457.6 RRP $37.95
All there is to know to efficiently repair microwaves, and
it is PRACTICAL, using only the bare minimum of
theory. With hundreds of detailed working illustrations
and photos and step-by-step instructions. 370 pages.

TROUBLESHOOTING WITH YOUR
TRIGGERED-SWEEP OSCILLOSCOPE

Goodman 0.8306.3891.1 RRP $35.95
Are you getting the most out of your oscilloscope? They
now do a lot more, but are easier to use—if you know
how! This is an invaluable practical guide to using all the
functions of your triggered-sweep oscilloscope, or to
choosing one if you’re thinking of buying. 309 pages.

PROJECTS AND GENERAL

GORDON McCOMB S GADGETEER S GOLDMINE!
55 SPACE-AGE PROJECTS

McComb 0.8306.3360.X RRP $35.95
If you’re ready to move up to (or already into) high-tech
experiments with lasers, fibreoptics, power supplies,
high voltage devices and robotics, look no further! Build
your own plasma sphere generator, make holograms
and lots more projects. 406 pages. Warning! High
voltages can be dangerous!

THE ROBOT BUILDERS BONANZA: 99 Inexpensive
Robotics Projects

McComb 0.8306.2800.2 RRP $29.95

This guide offers a complete collection of proven project

modules that you can mix’n’match to create an almost

endless variety of highly intelligent and workable robots.
For novices and intermediates, you’ll find all you need to
build a typical robot—body and frame, power and
locomotion, hands and arms, eyes and ears, navigation
and control. 326 pages.

ALARMS: 55 ELECTRONIC PROJECTS AND
CIRCUITS

Rakes 0.8306.2996.3 RRP $24.95
Smoke and fire alarms save thousands of lives every
year. Tripped burglar alarms scare off would-tfe
intruders. Now you can secure your home or car with
this book and its tips and advice for building and
installing each project. Also includes temperature, flood,
radiation alarm circuits and more. 170 pages.

HOME REMOTE CONTROL AND AUTOMATION
PROJECTS, 2nd edition

Horn 0.8306.2196.2 RRP $31.95
Complete instructions and diagrams for 77 projects to
make life easier! Plans include intruder detectors, flood
and temperature alarms and automated lighting. There
are also sections on potentiometer ICs, stepper motors,
timers and using personal computers for control. 301
pages.

DESIGNING AND BUILDING ELECTRONIC FILTERS

Horn 0.8306.3933.0 RRP $29.95

Whatever sort of filter you’re interested in, you’ll find it

here. Simplified maths with examples and practical

circuit plans show you how to build almost every kind of

filter, from passive low-pass to active band-reject, from

state-variable to voltage controlled and digital filters. 300

pages.

THE RADIO AMATEUR S DIGITAL
COMMUNICATIONS HANDBOOK

Mayo (KR3T) 0.8306.3362.6 RRP $28.95
Whether you're a beginner or an experienced packet
radio enthusiast, this handy guide has all the information
you need. All major digital modes are included, with
protocols and procedures. It also shows you how to
equip or improve your own station. 208 pages.

MASTERING TECHNICAL MATHEMATICS

Crowhurst 0.8306.3438.X RRP $47.95
Originally a 4-volume set, this book gives better
understanding by explaining how and why math
principles work. Includes step-by-step illustrated
instructions and alternative methods for solving
problems. A practical self-teaching guide to technical
mathematics—from counting to calculus. 586 pages.

All books are softcover.

Prices and availability are subject to change without notice.
RRP = Recommended Retail Price.

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* If not completely satisfied, books can be returned in resaleable condition within 21 days of date of invoice for a full refund.

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RRP$

MAIL or FAX TO: McGraw-Hill Book Company Australia Pty Limited Postage & Handling

4 Barcoo Street Roseville NSW 2069 A.C.N. 000 473 674 Telephone: (02) 417 4288 Facsimile: (02) 417 5687 92EA10 TOTALS

$6.00

Construction Project

HIGH QUALITY STEREO
AMPLIFIER USIHG VALVES - 2

In the first of these articles, the author explained the philosophy behind the project, and described in
detail the circuit design and operation. This month he moves on to cover the construction and testing
of the amplifier. As he explains, the design is quite straightforward and should not give any problems
providing you follow the steps described.

by TEAN Y. TAN, B.E. (Hons.)

To ensure that constructors don’t ex¬
perience any problems getting the parts
to build this amplifier (some of them are
now rather harder to obtain than they
once were!), I have made arrangements
to source them myself, and supply them
direct to readers as a kit.

Only the highest quality components
and parts are supplied, and the kit is com¬
plete as shown in the parts list. It even

includes a special chassis, manufactured
in Australia.

I estimate that builders with some con¬
struction experience should not take
more than 10 hours to build the amplifier.
The tools required for the construction
are a soldering iron, solder, screwdrivers,
a small adjustable spanner, a multimeter
and a jumper lead with alligator clips at
both ends. The use of the last item will

become apparent under the section on
safety precautions.

The kit can only be obtained directly
from Contan Audio; for further details
please refer to the end of this article.

Safety precautions

It must be strongly emphasized at this
point that builders must take due care
when constructing this project. Unlike

Here is a general view looking under the chassis. The output and power transformers are visible at the bottom, near the
rear, with the filter choke at upper right. The PC board at upper left supports all of the low level circuitry.

34 ELECTRONICS Australia, October 1992

other amplifier projects using solid state
components, the present design involves
very high voltages — 350V AC on the
secondary side of the power transformer
and as high as 500V DC for some of the
plate and screen wiring and components,
quite apart from the usual 240V AC on
the primary side of the transformer.

All of these voltages are potentially
very dangerous.

The following precautions should
therefore be taken before applying mains
voltage to the amplifier, and making sub¬
sequent measurements:

1. The mains earth should be connected
to the chassis, in a reliable and
secure fashion.

2. All of the 0V terminations shown on
the schematic as going to chassis
ground should be connected to the
chassis. This will be elaborated
upon in the next section.

3. The correct fuse must be inserted in
the IEC socket fuseholder.

4. Use only one hand when measuring
any voltages — preferably the right
hand. The left hand should not be
touching any part of the amplifier,
or any earthed metal objects. The
common terminal of the multimeter
is connected to the chassis ground
using the alligator jumper lead.

5. Switch off the amplifier before
making any adjustments — e.g.,
changing components, or correct¬
ing any faulty soldered joints in
the amplifier.

6. Do not plug in any valve when the
power is ON.

Always turn the power OFF before
plugging in any tube; if necessary
check the B+ voltage before plug¬
ging it in.

7. Do not make measurements unless
you are wearing suitable footware.
This means ideally rubber or plastic
soled shoes, although leather-soled
shoes are suitable if you are on a
perfectly dry floor.

The builder should make sure that he
or she takes the above safety precautions.
The project is designed so that if con¬
structed as shown, you should be able to
measure any voltages on the amplifier
without removing or touching any com¬
ponents, parts or the PCB. All the vol¬
tages are within easy access.

Construction

You are encouraged to build this
amplifier step by step, using the follow¬
ing procedure to reduce the risk of
making any mistakes.

By tackling the assembling in stages
and testing as you go, any problems
which may arise are likely to be isolated
and located easily, before they result in
any component damage.

To help you in assembling the
amplifier, we are providing a diagram
showing the location of all parts mounted
on the PCB (Fig.l), plus another showing
the wiring between the PCB and all of
the components mounted separately
(Fig.2). These plus the photographs
should make the assembly quite
straightforward.

STEP 1:

Mechanical assembly

First of all, mount the two pairs of
octal sockets for the output valves (V3
and V4) underneath the chassis, with the
socket rings and screws provided. Note
the correct orientation (Fig.2).

Then mount and tighten the following
components to the chassis:

A. The front panel.

B. The RCA input terminals.

C. The earth screw terminal.

D. The speaker terminals.

E. The DEC captive power plug and
fuseholder.

F. The power switch.

Here's a close up of the PC board assembly, with the four output valve sockets just below it. Note the way that the valve
heater wiring is twisted together, to minimise any external field and prevent hum injection into the signal circuitry.

ELECTRONICS Australia, October 1992

Valve Amplifier - 2

G. The volume control pot, if you are
fitting one.

H. The output transformers, together
with their protective covers
(provided). Refer to Fig.2 for the
correct transformer orientation.

J. The power transformer, again with

its protective cover. Fig.2 gives the
correct orientation.

K. The 8-way terminal strip, for sup¬
porting C8 and C9, etc. Make
sure that you scrape a small
amount of the lacquer away from
the inside of the chassis, around
each mounting hole, and use a ‘star’
lockwasher between each foot of
the tagstrip and the chassis, so that
when the mounting screws are
tightened, there is a really good
metal-to-metal contact via the lock-
washers and bared metal.

L. The filter choke LI. This mounts on
the end of the chassis; ensure that
the terminal connections are located
underneath and not exposed.

M. The main reservoir electrolytic
capacitors CIO and Cll, with the
rings and screws provided. Mount
the rings underneath the chassis.

N. The main rectifier bridge Bl. This
mounts under the chassis between
CIO and Cll.

Before mounting, bend each lead
carefully about 8-10mm from the
body, into a small loop (say 2mm
ID), to allow easy soldering of the
connection leads. Then cut off any
excess lead length. The bridge at¬
taches to the chassis using a single
machine screw, nut and lock washer.

This completes the assembly of the
main items, apart from the PC board.

STEP 2:

PCB assembly

A single PCB measuring 255 x 85mm
is used to mount the majority of the
smaller components, along with the
sockets for the input and driver valves
(VI, V2) for each channel. Note that the
components are mounted on the same
side as the tinned copper tracks, except
for the valve sockets which are mounted
on the reverse (top) side.

With reference to the circuit diagram
and Fig.l, fit and solder the components
in the following sequence:

A. All of the resistors, diodes and zener
diodes. Note that the power dissipa¬
tion for R1 and R2 exceeds 0.3
watts, under quiescent conditions,
so for adequate ventilation, bend the
leads of these resistors so that they

mount about 3mm up from the sur¬
face of the PCB.

B. The valve sockets. These mount on
the reverse side, orientated as
shown in Fig.l so that the pins pass
through the holes in the PCB and
solder to the pads on the copper side.

C. The BC546 transistors (one per
channel — Ql).

D. The bias trimpots P2 - P5. Fit the
centre two, P3 and P4 first, then the
outer P2 and P5. Each trimpot
should be mounted with its adjust¬
ment screw towards the front panel
andC12/C13.

E. All of the electrolytic, coupling and
bypass capacitors. Take care with
the polarity of electrolytics C5 (x2),
C12 and C13 — this is shown clear¬
ly in Fig.l.

With everything thus fitted to the
PCB, you should now make a final
check that everything is in its correct
place and orientated correctly.

Then you are ready to mount the com¬
plete PCB assembly under the chassis,
with the components facing inwards and
the valve sockets passing through the
clearance holes in the chassis.

Use the sticky tape provided as
spacing, and fasten the PCB to the
chassis firmly with the machine screws
and nuts provided.

STEP 3:

Hard wiring

You should now be ready for the ‘hard’
wiring — that which connects between
the major items, and between the PCB
assembly and the rest of the components.

The suggested sequence of wiring is as
follows. Note that pairs of wires should
be twisted together where appropriate,
and that although the description below
describes the wiring for one channel,
both need to be wired up. Fig.2 should be
used as a guide, along with the
photographs.

A. First fit the 240V AC wiring be¬
tween the IEC plug/fuseholder, the
On-Off illuminated power switch
and the primary connection lugs of
the power transformer. Make sure
that this wiring is all in suitable
cable, with mains-rated insulation.
Also fit the earth lead (green or yel-
low/green insulation) between the
IEC plug’s ‘E’ lug and the earth lug
at the LI end of the terminal strip,
so that it makes a reliable connec¬
tion to the chassis.

2. Connect the high voltage (350V AC)
secondary winding of the power
transformer to the bridge rectifier
Bl, as shown in Fig.2, and then

complete the HT supply wiring in¬
volving C8, C9, CIO and Cll, LI,
R29 and R30.

Double check your wiring, to make
sure you have not made any errors.
Do NOT connect the output of this
supply to the PCB, as yet.

The following step is advisable, but not
compulsory; it involves powering up the
amplifier at this stage, to check that the
correct HT voltage is being produced. If
you do this, first connect your multimeter
carefully between the chassis (earth lug
of the tagstrip) and the V side of CIO,
with the multimeter set to its 1000V DC
range.

Then connect the mains cord, and
apply the power. The meter should read
approximately 500V, if all is well with
your wiring. If the voltage is correct,
remove the power and allow the
capacitors at least 20 minutes to dis¬
charge before proceeding further.

The only way to avoid this wait is to fit
an additional temporary discharge resis¬
tor from the V termini of CIO to chas¬
sis, BEFORE applying the power for the
test

A 100k, 1 watt resistor used in this way
will reduce the capacitor discharge time
down to about two minutes. Don’t forget
to remove this resistor, though, after it
has done its job.

By the way, while you are carrying out
the above test, you can check that the
On-Off switch is illuminated when
power is applied.

3. Wire up the output valve heaters, for
V3 and V4 in both channels. Con¬
nect lugs 2 and 7 of each V3 socket
to the same lugs on the V4 socket in
the same channel, and then connect
pins 2 and 7 of the socket nearer the
power transformer, for each pair, to
the outer lugs of one of the 6.3V
heater windings (i.e., the ‘0’ and
‘6.3V’ lugs). In other words, the
heaters for the output valves of the
right channel go to one winding,
and those of the left channel to die
other winding.

Note that the centre-tap (CT) of each
heater winding on the transformer must
be connected via a short insulated
wire, to the ‘chassis ground’ lug of the
main tagstrip. The heaters for VI and V2
of each channel are then connected to the
output valve heaters for the same chan¬
nel.

Lugs 4 and 5 of each V1 /V2 socket are
connected together, and connect to say
lug 2 of V3 or V4, while lug 9 of V1/V2
connect to lug 7 of V3 or V4.

All of the heater wiring is shown in
basic form in Fig.2. However it is very
important to twist together each pair of

ELECTRONICS Australia, October 1992

ON/OFF
SWITCH

Use this overall wiring diagram as a guide in making the connections between all of the main items, and also
between the PC board and the rest of the circuit. Note that for clarity , the heater wiring is not shown here twisted
together. Note too , that the wiring for the optional volume control is not shown — but is clearly visible in the
photographs.

ELECTRONICS Australia, October 1992

Valve Amplifier - 2

(insulated) wires used to make the
various heater connections, from the
power transformer to the output valve
sockets, between the output valve sock¬
ets and to the VI and V2 sockets. This is
necessary to prevent induction of hum
into the signal circuitry.

4. Connect lug 3 (plate) on each V3
socket to the ‘A2’ lug on its cor¬
responding output transformer; then
connect lugs 4 (screen grid) on each
V3 valve socket to the matching
‘SC2’ lugs of the transformers, via
resistors R20. When this is done,
connect lugs 3 of the V4 sockets to
the ‘Al’ lugs of the matching output
transformers, and finally connect
lugs 4 of each V4 socket to the
remaining ‘SCI’ lugs respectively,
via resistors R21. Again these con¬
nections are shown in Fig.2.

5. Connect lugs 5 (control grid) of each
V3 socket to R16 of each channel,
on the PCB, and lugs 5 of each V4
socket to the corresponding R17.
Then connect lugs 1 (suppressor
grid) and 8 (cathode) together on
each V3 and V4 socket, and connect
each V3 socket’s lugs to the R25 for
that channel (on the PCB), and each
V4’s lugs to the corresponding R26.

6. Connect the ‘B+’ lug of each output
(O/P) transformer to the positive ter¬
minal of CIO.

7. The output transformers are op¬
timized for either eight ohms or
two ohm loads. (For those who
require four or 16 ohms, please
ask for a different transformer
type.) It is believed that the
transformers supplied will cater
for over 90% of users, as most

modem speakers are nominally of
eight ohms.

For eight ohm operation, connect the
two secondary windings of each output
transformer in series, as shown in Fig.2.
For two ohm speakers, the connections
should be connected to parallel — that is,
connect ‘O’ to ‘O’ and ‘OP1’ to ‘OP2’.

Once you’ve connected the two
output windings together in either
series or parallel, then wire them to the
speaker terminals as shown, and connect
each ‘common’ speaker terminal to the
chassis earth.

8. At this stage, DO NOT wire the
feedback (F/B) lugs of each out¬
put transformer to the PCB. This
is done later, after troubleshooting
the circuit.

9. Connect the ‘B+’ pad at each end of
the PCB (next to R22) back to the
positive terminal of reservoir
capacitor CIO. Also connect the ‘0’
pad at the centre rear of the PCB
back to the chassis ground lug of
the tagstrip.

10. Connect ‘55V’ and ‘0’ pads on the
PCB (between C12 and C13) to the
similarly marked terminals on the
power transformer.

11. Connect the RCA input connec¬
tors to the PCB inputs, using
shielded leads (outer braid to
earth). Note that when the
volume control pot is not fitted,
resistors R28 are connected across
the PCB input lugs along with the
leads from the input connectors.

12. Connect the earth terminal to the
chassis ground.

13. Connect the copper flux reduction
straps of each transformer (three
total) to chassis ground, also.

The amplifier should now be fully
assembled, but before going any fur¬

ther I suggest that you check the above
steps again to ensure that nothing has
been missed.

Testing time!

Now it is time for you to test whether
everything has been wired correctly. As
discussed earlier, the safe method to per¬
form any measurements is to have the
common terminal of the multimeter con¬
nected to chassis ground, via the aligator
jumper lead.

First, plug in the valves VI and V2 for
both channels. DO NOT plug in the
power tubes just yet Then apply power
to the amplifier, and the following vol¬
tages should be checked with the help of
the circuit diagram:

1. The B+ (at say the + terminal of
CIO) should be about +495V
DC +/-10V.

2. The B- (at the junction of Cl3,

D2 and R24) should be about -77 V
DC+/-2V.

3. The emitter voltage at each transistor
Q1 (where it connects to R15)
should about -50V DC +/-2V.

4. Pins 1 and 6 of V2 should about
+220V DC +/-10V DC. Note that
this voltage will change when the
power tubes are plugged in, as the
B+ drops. As discussed in part one,
the difference in voltage between
pin 1 and pin 6 can be as high as
20V DC, due to mismatch of the val¬
ves. By swapping the valves
around, it is possible to minimise
this voltage difference.

5. The bias voltage for each output
valve should be adjusted via the ap¬
propriate trimpot. Pots P3 and P5
control the bias current for the V3
valves, while pots P2 and P4 control
the bias for each V4. Before plug¬
ging in the output valves, the pots

Placement of all of the parts in their correct places on the PCB should be a straightforward job using this overlay diagram
as a guide. Note that all components except the valve sockets are mounted on the copper side.

ELECTRONICS Australia, October 1992

should be adjusted such that the
voltage at lug 5 of each output valve
socket measures approximately -
44V DC. This is to set the bias cur¬
rent for each output valve to not
more than 40mA when they are
plugged in.

When you have performed all of the
above tests and adjustments, you are
ready to turn off the power and plug in
the output valves. Then you can turn on
the power again, and after waiting for
them to warm up (allow say one
minute), re-check the main voltages.

With the output valves plugged in the
B+ at CIO will normally have dropped to
about +475V DC, while the voltage at
pins 1 and 6 of each V2 should be be¬
tween about+180V and +200V DC.

Trimpots P2, P3, P4 and P5 should
now be adjusted so that the quiescent
cathode current for each output valve is
set initially to about 30mA. The builder
can experiment with other current levels
later, once the amplifier is operational
(although I suggest that you do not use
currents higher than 60mA, as this would
considerably shorten valve life).

The easiest way to monitor the
cathode currents is by measuring the
voltage at each valve cathode (lug 8
on each V3/V4 socket) — this reflects
the voltage drop across the 10 ohm
cathode resistors R25/R26.

For 30mA, each trimpot should be ad¬
justed to produce +300mV at the ap¬
propriate cathode lug. Make sure you
check and if necessary adjust the voltage
at each of the four cathodes.

If all is well so far, you are now
ready to connect the negative feedback to
each amplifier channel. Turn off the
power, wait 30 seconds or so and then
connect the ‘F/B’ lug on each output
transformer to resistor R13 for that chan¬
nel, on the PCB.

Use insulated hookup wire, of course.
Then turn the power back on. If there are
no funny noises from the output trans¬
formers, then the polarity is correct.
Otherwise there is a 180% phase shift be¬
tween the output and input, resulting in
positive feedback.

Troubleshooting

If the above voltages are not right,
check the following:

1. If the B+ line measures zero volts,
check the mains fuse. If the fuse is
there but has blown, you may have
a short circuit somewhere or have
made a mistake in your connections.
If the fuse blows again, when you
replace it, there is almost certainly a
short somewhere. Check your
wiring around the rectifier bridge,

the polarity of all electrolytics (espe¬
cially C8, C9, CIO and Cll), and
the heater wiring.

PARTS LIST

Resistors

R1,R2 220k 1W 5% carbon

R3,R4,R5,R6,R9

1M0.25W1% metal film
R7.R8 100 ohms 0.25W 1% metal film

R10 510 ohms 0.25W 1% metal film

R11.R27 10 ohms 0.25W 1% metal film
R12 Ik 0.25W1% metal film

R13 22k 0.25W1% metal film

R14 56k 0.25W 1% metal film

R15 12k 0.25W1% metal film

R16.R17 2.2k 1W 5% carbon
R18.R19 470k 0.25W 1% metal film
R20.R21 Ik 1W 5% carbon
R22,R23,R24

10k0.25W1% metal film
R25.R26 10 ohms 1W 5% carbon
R28 100k 0.25W 1 % metal film

R29.R30 470k 1W 5% carbon

Capacitors

Cl ,C2 1 uF 250V polycarbonate

C3,C4 0.47uF 400V polypropylene

C5,C8,C9 47uF 450V electrolytic
C6 39pF ceramic

C7 0.68uF polypropylene

C10.C11 680uF 250VW electrolytic
(chassis mtg)

C12.C13 IOOuF 160V electrolytic
Semiconductors
D1 1N914/1N4148 signal diode

D2 1N4004 1 A/400V rectifier

B1 BR1010 10A/1000V bridge

Z1 1N971B 27V/400mW zener

Q1 BC546 NPN transistor

Valves

VI 12AX7/ECC83 dual triode

V2 12AT7/ECC81 dual triode

V3.V4 6CA7/EL34 power pentode

Miscellaneous

T1 Power transformer, with cover

T2 Output transformer, with cover

LI Filter choke, 1.5H

PI Dual ganged 100k log pot,

matched

P2-P5 50k 0.25W multi-turn trimpot

FI I EC captive mains plug

with 1A fuse

SW1 SPST 250V mains switch

with neon

Four octal valve sockets; four miniature
9-pin valve sockets; four insulated screw
terminals (two red, two black); two RCA
audio sockets; one screw terminal for
earthing; mains cord with 3-pin plug and
I EC socket; one 8-lug tagstrip for mount¬
ing C8, C9 etc; hookup wire, shielded
wire, mounting clips for large
electrolytics, nuts, bolts, lock washers,
solder etc.

If the B- line measures a positive volt¬
age instead of the correct negative volt¬
age, you have probably wired D2 the
wrong way around. This may have
caused damage to either D2 or C13.

2. If the voltages at pins 1 and 6 of V2
are too high, check that your heater
wiring is correct — there should be

6.3 V AC between pins 4 and 5 and
pin 9, for each of valves V1 and V2
in each channel. Also check that the
bias current is correct, by checking
the correct orientation of zener
diodes Z1 and signal diodes Dl, and
each transistor Ql. The voltage
across each resistor R15 should be
about 27V DC+/-0.5V.

3. If positive feedback occurs when
you connect the feedback loops,
then change over the wiring at the
O/P transformer. That is, swap the
wires connecting to the A1 and A2
lugs, and also those connecting to
the SCI and SC2 lugs. Normally
this should not be necessary.

Listening tests

Now that you have finished the con¬
struction and testing of your amplifier, it
is time to reap the reward and listen to it.

At normal listening levels, the
sound should as described in part
One. Otherwise, there is something
wrong with your construction.

The slight brightness reported in part
one of these articles is mainly due to the
output valves. After replacing them the
brightness should disappear altogether.
The sound is now more balanced and as a
result there is better imaging.

For those builders who like to experi¬
ment, there are a number of options
worth exploring. Examples include set¬
ting the output valves for Class A opera¬
tion and connecting them for triode
operation. These options were discussed
in part one. Free advice will be given to
those who purchase the kit.

I hope you will enjoy building and
listening to this amplifier, as much as I
have enjoyed designing, testing and
manufacturing it.

Obtaining a kit

As noted in the first article, kits for the
Stereo 80 valve amplifier are only avail¬
able from Contan Audio, of 37 Wadham
Parade, Mount Waverley, Victoria 3149;
phone (03) 807 1263.

The price of the kit, including all parts
and valves, is $999 plus postage without
volume control, or $1035 with the spe¬
cial matched dual-gang volume control.
These prices include sales tax.

If required, the amplifier can alterna¬
tively be supplied fully assembled and
tested for $1249 without volume control,
or $1284 including volume control.

Individual parts for the design are also
available, such as the output and power
transformers, chassis, valves etc. Please
ring for prices. All parts are guaranteed
for one year, except for the valves which
are only covered for six months. ❖

ELECTRONICS Australia, October 1992 39

FORUM

Conducted by Jim Rowe

A reader who’s really put some
speaker cables under the microscope!

As I mentioned last month, our discussion of ‘low noise’ power cables a couple of months ago
prompted a reader to send in a report of some fairly extensive testing he did to compare the
performance of one of those much-vaunted fancy speaker cables with a couple of standard low
cost cables. I think you’ll find both his tests and the results quite interesting...

The reader concerned is Mr Brendan
Jones, of Bondi Junction in Sydney, who
is a professional engineer working in a
fairly large local R&D laboratory. He ex¬
plains in his cover letter that he decided
to carry out the tests on speaker cables
after being annoyed by the ‘endless and
ridiculous claims’ being made for them.
The idea was to put three types of cable
through a series of comparative tests, to
see just how different they really are.

The tests Mr Jones applied to the ca¬
bles were those suggested by fellow
readers of the ‘Internet’ electronic news-
groups ‘rec.audio’ and ‘rec.audio.high-
end’, to which he apparently belongs. He
notes that the cables were tested from a
purely electrical point of view; there
were no listening tests, due to the great
difficulty in setting up a valid subjective
test.

But I think that’s enough introduction
from me — let’s give Mr Jones the floor.
His report is quite long, and we don’t
have space to present it in its entirety;
however I think we can present enough
of it to make the exercise worthwhile.
Here’s his introduction:

In some hi-fi circles, much attention
has been given to speaker cables as a
possible source of distortion or coloura¬

tion in delivering the signal from the
power amplifier to the speakers. This has
led to a number of high-end speaker ca¬
bles being designed, that are claimed to
overcome the inherent deficiences in
their cheaper counterparts, and hence
deliver a purer, cleaner and less dis¬
torted sound.

These high-end cables use materials
and designs, such as special dielectrics,
special design and arrangement of con¬
ductors, and conductors made of special
forms of copper (e.g., oxygen-free cop¬
per or copper with aligned ‘crystals'),
that are claimed to give better perfor¬
mance.

The deficiencies in cheaper cables are
often said to include:

• High resistance per unit length;

• High dispersion (frequency spread);

• No consideration of the skin effect;

• Poor frequency response;

• Poor transient response.

In order to test the significance of each
of these parameters, three similarly con¬
structed cables, but cables of quite dif¬
ferent ‘reputation' were electrically
tested to ascertain their comparative
performance using very accurate elec¬
tronic test and measurement equipment.
The cables chosen were Monster

Cable (around $10 per metre), 7.5A
240V mains flex (around $1 per metre),
and a cheap generic figure 8’ speaker
cable (most commonly used for speakers,
around 40 cents per metre).

All of these cables consist of helically
wound fine wires in each bundled con¬
ductor, and each bundled conductor is
insulated with some form of plastic or
dielectric coating. The bundled conduc¬
tors are then run parallel to each other
and separated by a certain distance, in
what is known as a figure 8' configura¬
tion.

Parameters tested

Essentially there are four electrical
tests that can be performed, that will pro¬
vide a good basis for comparison of the
three cables. These tests are:

(1) DC passive measurements

(2) Frequency and phase response

(3) Transient response

(4) Power compression

As the cable samples used were differ¬
ent lengths (from 25 to 45 metres), the
results have been expressed as a ‘per
unit length' measure, to enable direct
comparison wherever possible.

To perform the tests, an extensive
array of quite accurate and powerful test
equipment was assembled. The equip-

ELECTRONICS Australia, October 1992

merit used in each test segment is listed
below:

(1) Fluke 77 multimeter; Parameters
7080B multimeter; GW dual tracking 3A
laboratory power supply; HP8753B
3GHz network analyser.

(2) HP8753B 3GHz network analyser;
HP54110D 1GHz digitising oscillo¬
scope; Tabor 8200 20MHz function gen¬
erator; Philips PM2554 2Hz-12MHz AC
millivoltmeter.

(3) Tektronix CSA803 communications
signal analyser with TDR head.

(4) GW dual tracking 3A laboratory
supply; Fluke 77 multimeter.

Tests and results

The first tests Mr Jones carried out
were those for the passive parameters of
the cables — DC resistance, capacitance
and inductance.

DC resistance was measured using the
setup shown in Fig.l, using 3.5-digit
Fluke 77 DMM’s to measure the voltage
drop of the cable at various current lev¬
els. The various readings were then aver¬
aged. Here’s how Mr Jones’ describes
the results:

The Monster Cable had the lowest DC
resistance per metre, of 15.9mQJm, but
not significantly lower than the mains
flex, which came in at 22.0mQJm. The

generic figure-8 cable fared poorly at
114.2mDJm.

However the power lost in a speaker
cable is not great (unless the cable run is
very long) as a total cable resistance of
around 0.1Q. for four metres of low resis¬
tance cable is fairly insignificant com¬
pared to the nominal speaker impedance
of 80. (although the speaker impedance
may vary greatly from this and have both
capacitive and inductive components).

Lower cable resistance will largely
manifest itself as a slight volume in¬
crease, as less power is lost in the cable.
However, depending upon the complex
source impedance (of both the power
amplifier and the speakers), it may also
effect the damping ratio of the speakers
and ' muddy 9 the sound. Hence a rule of
thumb would suggest that the lower the
resistance of the cable, the better.

The capacitance of each cable was
then measured, using the capacitance
range of the Parameters multimeter. The
results were:

Monster Cable: 49.8pF/m
Mains flex: 82.7pF/m

Figure 8: 45.9pF/m

Finally the inductance of each was
measured at 300kHz, using the H-P net¬
work analyser. As Mr Jones notes:

This measurement is valid because the

cables were short enough not to behave
like transmission lines until about
10MHz. The wavelength of a 300kHz
signal in these cables is around 700 me¬
tres, much longer than the 3 to 4m
lengths used, and so any antenna or
transmission line effects are negligible.

The measurements obtained were
699nH/m for the Monster Cable,
587nH/m for the mains flex and
141nH/m for the figure-8.

Next, Mr Jones measured the fre¬
quency and phase response of each cable
over the range 10Hz - 10MHz, using the
setup shown in Fig.2. The Philips AC
millivoltmeter was used to measure the
amplitude response, and the DSO to
measure the phase response. Mr Jones
notes here that:

The T junction does not disturb the
time delay measurements, as the input
impedance to the AC millivoltmeter is
1M. In the time delay measurements,
there was a phase offset due to the differ¬
ence in cable path lengths between the
signal generator and the oscilloscope.
This phase offset was calculated and re¬
moved from the results to give a true
indication of the phase response of the
cables alone. Note that at low frequen¬
cies, the phase offset became so small as
to be difficult to measure accurately.

ELECTRONICS Australia, October 1992

FORUM

Hence below about 10kHz, the results
were so close as to be virtually unmea¬
surable on the equipment used.

The frequency and phase responses so
measured are graphed in Figs.3 and 4. It
is evident from these graphs that the ca¬
bles perform so similarly in the audio
band (20Hz to 20kHz), with zero phase
ripple and around 0.05dB attenuation
ripple, that it is difficult to conceive of
there being any audible difference on the
basis of frequency response alone.

Note that a 0.05dB attenuation ripple
means that the variation in povser deliv¬
ered to the speaker over the audio band
is around 0.01%. It is very unlikely that
this would be audible. Also, the ripples
were so similar for each cable (mains
flex was marginally the best), that no one
cable has an advantage over another, in
this respect.

It is also possible that this ripple is an
artifact of the AC millivoltmeter preci¬
sion. This is accurate tol% from 10Hz to
400kHz, 2% from 400kHz to 6MHz and
4% from 6MHz to 12MHz.

While on the subject of frequency and
phase response, Mr Jones also checked
the dispersion characteristics of the three
cables:

It is often claimed that the higher fre¬
quencies in an audio cable travel faster
than the lower frequencies, and that this
leads to signal ‘smearing unless the
cable is designed to carry the higher fre¬
quencies on a longer physical path. This
frequency smearing effect is called dis¬
persion.

Electromagnetic theory indicates that
firstly, it is not possible to carry different
‘parts’ of the audio signal on different
conductors, and secondly that for such a
frequency smearing to be audible, the
required difference in propagation

speeds across the audio band are ridicu¬
lously large. For example, if a 0.1° phase
shift of a 20Hz signal relative to a 20kHz
was audible, this would require the 20Hz
signal to arrive at the far end of the cable
14us after the 20kHz signal. In 14us light
travels 4.2km, so if the 20kHz signal
travels at near the speed of light, this
frequency smear is not even possible un¬
less the speaker cable is longer than
4.3km!

The units of dispersion are s/Hz, and
can be calculated by dividing the mea¬
sured time delay difference over the cor¬
responding frequency difference.
Dispersion can also be expressed on a
per-unit-length basis, as s/Hz/m.

All the cables had EXTREMELY small
values of dispersion, of the order of pico¬
seconds/Hz. This translates to a worst-
case phase shift of a 20Hz signal to a
20kHz signal of around 0.1 MILU de¬
gree per metre of cable. It is EX¬
TREMELY unlikely this would be able to
be detected by the human ear.

The figure-8 cable had the lowest dis¬
persion of 0.44ps/Hz/m, with Monster
Cable at 0.66pslHz/m and mains flex at
0.79ps/Hz/m.

The only conclusion possible is that
audible ‘cable smear’ is extremely un¬
likely in copper cables at audiofrequen¬
cies.

Transient response

Mr Jones then measured the transient
response of the cables, using the
Tektronix communications signal an¬
alyser with time-domain reflectometry
(TDR) head. This produces a 10kHz
square wave of IV p-p amplitude, and a
pulse risetime of 20ps (picoseconds).
The idea was to measure the signal re¬
flected from the end of a mismatched

cable, to determine the propagation
delay, characteristic impedance and tran¬
sient response to an applied ultra-fast
risetime pulse.

The cables were connected to the TDR
head one at a time, initially with the far
end open circuited. By measuring the re¬
flected signal ‘round trip* time delay and
dividing by twice the length of the cable,
its propagation velocity could be deter¬
mined. The Monster Cable turned out to
have the highest propagation velocity, at
71.8% the speed of light, with the mains
flex next at 70.6% and the figure-8 slow¬
est at 66.1%. As Mr Jones observes these
figures ‘are really of no consequence in
an audio system, but they are
interesting’.

The free end of each cable was then
connected to a sampling head on the
Tektronix, to measure the transient re¬
sponse of each cable to the 20ps risetime
IV p-p signal. Mr Jones reports here:

The results showed very little differ¬
ence in the transient response in any of
the cables tested. The cable rise times
were 3.2ns for the Monster Cable, 2.2ns
for the mains flex and 23ns for the fig¬
ure-8 cable. These rise times mean that
the cable response is adequate out to the
tens of megahertz region, some nine oc¬
taves higher than the limit of human
hearing.

The step responses showed the most
marginal of ringing, the frequency of
which would be very much higher than
what the ear could hear. Hence the tran¬
sient response appears to be an irrele¬
vant factor in these cables.

Power compression

Mr Jones* final tests were designed to
see whether any of the previous behavi¬
our, which was all measured at relatively
low voltage and current levels, might
vary at the current levels which would
occur in a typical hifi system. As he

Cable Attenuation vs Frequency Cable Phase vs Frequency

Flg.3 at left shows the measured frequency responses of the three cables , with their phase responses at right.

42 ELECTRONICS Australia, October 1992

Cable Resistance vs Current Cable Resistance vs Current (expanded)

Fig.5(a) at left shows the variation in DC resistance/metre of the cables, at different levels of direct current , measured by
Mr Jones to determine the likelihood of power compression. Fig.5(b) at right is an expanded view of the lower two curves.

points out, a power of 100W delivered
into an 8 Q, load requires an RMS current
of 3.5A — so speaker cables typically
carry quite appreciable currents.

First of all, the DC resistance per metre
of the cables was measured at various
current levels, from low levels up to a
maximum of 3.11 A (the maximum avail¬
able from his supply). This corresponds
to nearly 80W of power into an SO. load.

The results are plotted in Fig.5(a) and
(b), and they show virtually no non-lin¬
ear changes (the irregularities at low lev¬
els are due to limited precision in the
voltmeter used). The figure-8 cable
shows a 4% increase in resistance over
the current range, while the other two
show only about 1-2% increase — as
well a having a significantly lower resis¬
tance anyway.

As Mr Jones notes, this result does not
take into account any effects which
might conceivably occur when AC is
flowing, instead of DC. He then pro¬
ceeds to discuss the possibility of non-
linearities due to skin effect, as some
people have suggested:

The formula for skin depth in a good
conductor is given by reference (1) as:

8 = iHnfixa

where f is the frequency, p. is the perme¬
ability of the material (for a conductor,
\io = 4n*10~ 1 Hlm) and c is the conduc¬
tivity (for copper = 5.8*10 7 S/m). 8 in
metres, and is the depth at which the
electric field inside a conductor falls to
He, or 36.8% of its surface value.

At DC, the skin depth is infinite and
hence the current density is uniform
across the conductor. Skin depth is NOT
dependant upon the absolute level of
current, unless the media becomes non¬
linear.

At 20Hz the skin depth in copper is
14.78mm, and at 20kHz it is 0.467mm.

As the individual conductors in the ca¬
bles are a minimum of 0.06mm in radius,
this means that at 20Hz the current den¬
sity at the centre of the conductors is
99.9996% of that at the skin, whilst at
20kHz this drops to only 99.987%.

Thus the cables should behave as es¬
sentially uniform conductors all the way
to 20kHz, and essentially no different to
the way they behave at DC. Hence we
can conclude that our low current mea¬
surements should still be valid at high
currents up to at least 1MHz, where the
skin depth becomes equal to the individ¬
ual conductor radius.

However what is the effect of the pres¬
ence of the other conductors in each
bundled conductor? If the individual
conductors have good electrical contact
with each other (which they will, unless
the strands are individually insulated, as
in Litz wire), then each bundled conduc¬
tor will behave similarly to a solid con¬
ductor of the same size. This makes a
nonsense of the claim that staggered
strand sizes are used to carry the differ¬
ent ‘parts of the audio signal — they
effectively behave as a single conductor.

Conclusions

Mr Jones offers the following com¬
ments in his conclusion, at the end of the
report:

The results indicated that of the five
alleged deficiences in cheaper cables,
only the first — higher resistance — is
borne out by electrical measurement and
electromagnetic theory. Claims with re¬
spect to the skin effect, cable dispersion,
transient response and frequency re¬
sponse appear to be unsubstantiated.

Of the parameters tested, only the pas¬
sive parameters (resistance, inductance
and capacitance, or R,L and C) appear
to be significant in an audio system, and

of these resistance is probably the most
important. Choosing a cable with a
lower resistance will marginally improve
the power transfer to the speakers and
hence result in a slight increase in the
speaker volume. This slight increase in
volume is probably what most people
will judge as ‘better’ in the allegedly su¬
perior cables.

A low resistance cable will also make
the amplifier source appear ‘stiffer (i.e.,
give it a source impedance closer to
zero), and hence make the amplifier
more effective in driving the speaker
cones faithfully.

The results suggest an interesting fol¬
low-up experiment. The R, L and C char¬
acteristics of a high end cable could be
measured and effectively simulated with
a lumped model consisting only of pas¬
sive components, and then a double¬
blind test performed to see if audible
differences could be detected between
the high-end cable and its passive com¬
ponent model. If the results were nega¬
tive, it would appear that the passive
parameters are the ONLY parameters of
importance, and hence any desired cable
performance could be emulated by de¬
riving the passive model.

In conclusion, if you want to choose a
low resistance cable, then 10A or 15A
mains flex or any other suitably high
current capacity cable with large con¬
ductors or a large number of conductors
will most likely perform more than ade¬
quately — and at a much lower price
than Monster Cable or any other high
end speaker cable.

In high-end systems where the L or C
may be important, the source (amplifier)
and load (speaker) response could be
measured and then the R, L and C of a
cable designed to give the overall fre-
(Continued on page 93)

ELECTRONICS Australia, October 1992

Cellular radio technology update:

AOTC'S NEW CELLULAR
MOBILE NETWORK - 2

In this second article explaining how the digital GSM cellular radio telephone system operates, the
author describes the techniques that GSM uses to extend the battery life of mobiles, and also to
overcome interference and minimise fading effects. He also explains why GSM offers far higher
security than AMPS, and the ways in which it offers greater operational flexibility.

Part of a GSM base station. The two plug In cards at far left are part of the radio
transmitter and control channel circuits, while the large card in the middle
contains the radio receiver. The seven cards to the right of this are identical, and
each control one of the eight time-slots on a GSM frequency.

by ROBERT OWEN

Unlike the current cellular mobile
telephone system AMPS, which uses
25kHz FM radio channels with each
channel being able to transmit only one
voice call, the GSM system will use
200kHz digital channels, with each digi¬
tal channel being able to handle eight
simultaneous voice calls.

The method GSM uses to digitise the
eight voice calls is similar to the way the
public telephone network digitises and
multiplexes 32 voice circuits over one
pair of wires — see ‘Our Evolving Net¬
work of Communications’ in Electronics
Australia , November 1991 to January
1992.

Suppose we have a cell radius of
30km. A transmission burst from a
mobile station (a mobile phone) 30km
from the base station (the cellular
network’s receivers and transmitters)
would arrive 100 microseconds later
than would be the case if the mobile sta¬
tion were located near the base station.
To put a long guard period between each
of the eight bursts would be inefficient,
but on the other hand we cannot allow
bursts from distant mobile stations to
overlap bursts from nearby stations.

What GSM does is to measure the
round trip delay from the base station to
the mobile station and back to the base
station — for a mobile 30km away, this
would be about 200us.

The base station then sends a control
message to the mobile station instructing
it to retard or advance transmission of
each burst, so that bursts arrive at the
base station without overlapping ad¬
jacent time slots.

Using this technique, the time at
which a burst arrives at the base station
can be controlled to within 2us — ap¬
proximately half a bit period.

ELECTRONICS Australia, October 1992

Even though frequencies are re-used
every three cells, there is a possibility
with high power mobile stations that a
radio burst will travel across many cells
and interfere with other users on the
same frequency. To overcome this, the
base station measures the signal strength
of each mobile station operating within
its cell, and instructs each station to
lower its RF output power to a level just
sufficient for the call to be clearly
received by the base station.

Obviously, both timing and power out¬
put need to be adjusted continually as a
mobile station moves through a cell. In
order to perform this, each of the eight
voice circuits in a GSM channel has a
control circuit for this type of control in¬

formation to be passed from the base
station to the mobile, and vice versa.

The majority of mobile station trans¬
missions will involve speech. Further¬
more, because only one person at a time
will be speaking, on average each one¬
way circuit will only be carrying voice
for less than half the time.

To exploit this, the mobile station will
contain a ‘voice activity detector’ that
will distinguish between speech and
silence (or background noise). Usually,
only when the mobile subscriber is
speaking will the mobile station transmit
signals to the base station. Most of the
rest of the time the mobile station will
not transmit RF.

This gives two major advantages.

Firstly, the time during which a mobile
station can interfere with another station
is approximately halved.

Secondly, for small hand-held phones
where most of the power is consumed by
the RF amplifier, battery life will be sig¬
nificantly extended.

If GSM used this technique alone,
during silent periods the listener would
hear nothing — not even the background
noise associated with the distant sub¬
scriber. Switching from speech with its
background noise to silence has been
found to be highly disturbing to the lis¬
tener. This is particularly the case as
background noise from a mobile sub¬
scriber is likely to be high.

To overcome this, the voice activity
detector extracts the background noise
from the speech and periodically trans¬
mits to the base station the value of the
background noise. Even though the
value of the background noise is only
transmitted over the RF circuit peri¬
odically, the base station will send to the
listener regenerated background noise
during the time that the other person is
not speaking.

Anybody who has listened to FM
radio while driving will have ex¬
perienced fading due to multipath inter¬
ference while passing large buildings.
Fading during a cellular call is irritating
to the listener and can result in calls
being dropped.

Fortunately, fading is localised and
does not usually extend more than half a
wavelength. Thus at 900MHz — the fre¬
quency at which GSM operates —

GSM: A technical summary

In Australia as well as in Europe, the fre¬
quency ranges 890-915MHz and 935-
960MHz have been reserved for GSM. The
lower of these frequency bands is used for
transmissions from mobile stations to base
stations, while the higher band is used for
base station to mobile transmissions. If a
mobile station uses a frequency F(ms) to
transmit to a base station, that base will
transmit back to the mobile at a frequency
F(bs) which is exactly 45MHz higher.

i.e., F(bs) = F(ms) + 45MHz

For example if the mobile transmits on
900MHz, the base station will ‘reply’ on
945MHz. The same time slots are used in
both directions.

A frequency band in GSM is 200kHz wide.
Therefore the theoretical number of frequen¬
cy channels is:

(915 - 890) * 1000/200 + 1 =126

In practice not all of these channels are
available, since the top and bottom 200kHz
channels are used as guard bands. Hence
only 124 frequency channels are available.

Because each frequency channel can
support eight time slots, the total number of
simultaneous voice coils that can be hand¬
led are thus 124 x 8 = 992.

If an area is covered by repeating a pat¬
tern of seven cells, then each cell will be

different time slots on the same
frequency. Note that only one direction
Is shown.

fading is unlikely to extend more than
17 metres.

Although this amount of fading is ac¬
ceptable for vehicles travelling at high¬
way speeds, some vehicles may remain
in a particular frequency’s fade region
for some time — for instance while
waiting at traffic lights, while moving
slowly during rush hour or while stand¬
ing with a hand-held phone.

To minimise the affect of fade, GSM
designers have introduced a technique
called frequency hopping . Because any
fading at a particular location is likely to

able to support 992/7 = 141 (approximately)
simultaneous calls. This is because a fre¬
quency cannot be re-used in any of the
other six cells making up the seven-cell pat¬
tern.

A base station typically has a cell radius of
35km and has an RF power output of 10
wa tts — although this could go up to 50
watts over difficult terrain or over the very
large radius cells expected in rural areas. A
hand-held mobile station used in a very
small street-sized cell (called a micro-cell)
would typically have an RF power output of
about lOOmW.

In order to keep the transmitted power of
a mobile station to a minimum, a base sta¬
tion can command a mobile to reduce its
power output.

A GSM mobile can alter its power output
at the rate of 2dB every 60 milliseconds.
Thus a mobile station can step through a
complete range of 15 steps (30dB) in less
than a second (900ms).

Unlike the public switched telephone net¬
work, which uses 64kbps digital channels to
transmit speech, GSM uses voice compres¬
sion and a data rate of 13kbps per time slot,
to transmit speech with the same quality as
the PSTN. GSM uses quadrature phase-
shift keying (QPSK) to modulate the digital
data onto the RF carrier.

be restricted to a single frequency, it will
probably only affect a single mobile sta¬
tion that happens to be located there.
Base stations, instead of keeping mobile
stations on a single frequency, will ran¬
domly change the transmit and receive
frequencies for all mobile stations
within a cell to other frequencies — 217
times each second.

Using this technique the effect of fade
will be different for every burst; signal
drop-outs will thus be short and can be
compensated for by error correction
techniques. Frequency hopping is inde¬
pendent of the change in frequency that
occurs when a mobile station moves
from one cell to another during a call.

Because fading at a particular location
is unlikely to extend more than half a
wavelength, at every base station there
are two receiver antennas with a single
transmitter antenna located between
them. The two receiver antennas are
used so that if one of the antennas is in a
fade region, hopefully the other antenna
will be able to pick up the mobile
station’s signal.

The fade pattern around a city due to
signals from a base station is likely to be
static, because the base station’s antenna
and large buildings are in fixed loca¬
tions. Moving trains or large trucks
could, however, cause temporary fading.
At the base station’s antenna, however, a
particular frequency could fade in and
out as the transmitting mobile station
moves around. Fade and radio cover are
the two most difficult problems that cel¬
lular radio engineers need to consider
when planning a network.

One of the problems with the analog
AMPS cellular mobile phone system
was security. To encrypt an analog voice
circuit was too expensive to be practical,
and anybody could listen to a mobile
phone call with a correctly tuned
receiver. With GSM, however, the digi¬
tal radio transmission makes encryption
very simple. .

Whenever a mobile station makes a
call, the relevant base station sends a
message to a central database requesting
the encryption algorithm unique to that
mobile station. This encryption algo¬
rithm is already stored in the memory of
the mobile station. The encryption algo¬
rithm is then used to encrypt voice be¬
tween the mobile station and base
station.

If the subscriber passes through
several cells during the course of a call,
the encryption algorithm is changed
automatically every time the mobile sta¬
tion is handed over to the new base sta¬
tion. Also, if a mobile station transmits
in the same cell for a long period, the

ELECTRONICS Australia, October 1992

AOTC’s new cellular mobile network - 2

Fig.5: With GSM, the speech links involve coding and Fig.6: The hypothetical shape of each ‘cell’ is hexagonal
encryption as well as modulation on the transmit side, and while the optimum shape is circular: The actual shape of
decryption and decoding in addition to demodulation. cells is neither, of course, but varies considerably.

encryption algorithm is again changed
periodically. Encryption, together with
random frequency hopping, makes un¬
authorised interception of GSM calls
very difficult.

Another problem with AMPS has been
using the system to transmit data instead
of voice. Because one AMPS call took
up a whole RF channel, a break in trans¬
mission would disrupt any data being
sent.

Every time a mobile station moved
from one cell to another there would be
a momentary break in transmission as
the mobile station stopped communicat-

NOTES & ERRATA

STOP PRESS: A $40 RECEIVER
FOR WESAT RECEPTION!

Have you been interested in trying to
receive weather satellite images, but put
off by the price of a suitable receiver?

Well, your problems appear to be
solved. Tom Moffat, who designed the
Wesat decoder described in our June-
July-August 1992 issues, reports that he
has discovered a readily-available re¬
ceiver which is fine for Wesat reception,
but costs only $39.95.

The receiver is the Digitor Multi-
Band unit sold by Dick Smith Electron¬
ics, as catalog number D-2838. Tom has
found that this set not only tunes the
vital 137MHz band, but has adequate IF
and FM detector bandwidth to give un¬
distorted reception of Wesat signals.

Tom says the set’s sensitivity isn’t
quite up to the job, but if used with the
WIA ‘VK5’ preamp as discussed in the
August article, it works surprisingly
well with Wesat signals in the sub-mi¬
crovolt range.

Currently Tom is testing the Digitor
set further, and is also on the lookout for
other low cost sets that may be suitable.
We hope to publish the results of his
investigations soon, so stay tuned!

ing with one base station and started
communicating with the new base sta¬
tion. Although the break in transmission
was fairly quick — it can be detected by
a careful listener on a voice call — it
was long enough to disrupt a call that
involved sending data.

With GSM, however, the digital trans¬
mission method ensures that any data
being transmitted remains intact and that
there is no break in continuity during
handoff. This, together with other tech¬
niques such as error detecting codes, has
ensured that GSM mobile stations can
be used to transmit faxes and for other
forms of data communications. Indeed,
GSM is designed to be compatible with
ISDN and can transmit data to or from a
mobile station at 9.6kbps.

With the older AMPS, obtaining a
mobile station was part of the subscrip¬
tion to the service — every subscriber
had his own mobile station for personal
use. Information such as the subscriber’s
identification number was stored on
PROMs within the mobile station. Ob¬
viously this situation was inconvenient
as it did not allow subscribers to use
other mobile stations to make calls.

With GSM, the mobile station will not
contain any information unique to a sub¬
scriber; instead, each subscriber will be

AMPS: Technical basics

The frequency bands used for the cur¬
rent AMPS analog cellular phone system
are 825-845MHz (mobiles to base) and
870- 890MHz (base to mobiles). As with
GSM, base stations return a call from a
mobile on a frequency exactly 45MHz
higher.

The AMPS system uses frequency
channels 25kHz wide. Hence there are a
theoretical total of

(845 - 825) * 1000/25 + 1 = 801
available frequency channels. Only one
voice call may be made per frequency
channel, in any adjoining group of cells.

The AMPS system uses analog FM
transmission.

given a ‘smart card’, called a Subscriber
Identity Module Card , which can be in¬
serted into any GSM mobile station in
the same way that a banking card is in¬
serted into an automatic teller machine.
It will be the smart card that contains the
subscriber’s personal identification
number, encryption algorithm and
charging information.

Using a smart card makes the GSM
system much more flexible for sub¬
scribers. For example, a GSM mobile
station could be installed in every taxi;
all the passenger would need to do to
make a phone call would be to enter his
smart card into the mobile station and
any calls made would be charged to his
own account.

Also, by inserting his smart card, the
GSM system would know where the
subscriber was located and route any in¬
coming calls to the taxi’s mobile station.

So far we discussed the use of GSM
for both voice and data communications.
Another feature soon to become avail¬
able is the Short Message Service, which
allows a caller to send to the mobile sta¬
tion a short alphanumeric message up to
160 characters in length. The Short Mes¬
sage Service is thus a form of paging.

If the message is being sent to a
mobile station that has been turned off or
is out of radio range, the cellular system
will store the message and transmit it to
the mobile station when they resume
contact with the network.

In these two articles we have seen how
the new GSM system will considerably
increase the sophistication of AOTC’s
cellular radio network. To the subscriber
it will give better speech quality, greater
reliability and a wider range of features;
to AOTC it will give better frequency
usage and a more manageable network.

Australia, by being one of the first
countries in the world to implement
GSM is again showing itself to be a
leader in telecommunications. ❖

ELECTRONICS Australia, October 1992

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READER INFO NO. 9

Moffat’s

Madhouse...

by TOM MOFFAT

A musical battle of the sexes

How many of you readers out there
own big stereos? Plenty, I’ll bet. A lot of
interest in this magazine comes from
people wanting to read about, and build,
fine audio equipment. My own stereo
amplifier is one of the Electronics
Australia Playmaster kits, the MOSFET
amp from (as I remember) 1983. It’s get¬
ting a bit long in the tooth now, but it’s
still an excellent performer.

The amp is hooked to a pair of
Australian-made Leak speakers which
are even older — around 1968 vintage.
Back then, I was working for GTV-9
television in Melbourne, where the
Leaks were being used as studio
monitors. I wanted the best, so I got
Leaks too. Since then I’ve seen and
heard lots of pretty flashy speakers in
hifi shops, but nothing matches the
Leaks in my opinion. So they’ll be stay¬
ing around for a while longer.

Feeding the amp is a collection of
audio gadgets — an AM-FM tuner, a
stereo video, a cassette deck, and a Sony
CD player which I believe was the third
unit to be imported into Tasmania. The
thing cost me a fortune, but I just had to
be among the first! When I first had my
CD player, everyone else thought CD’s
were weird...

The Leak speakers are very efficient
when compared with today’s units, so
even with the 25 watt Playmaster amp
the whole system packs a pretty big wal¬
lop. That’s a shame, because I seldom
get to use it to its full capabilities. The
problem, in my house, is women.

We recently acquired a bass guitar
which now joins our musical menagerie
— including three other guitars, one
flute, one accordion, two synthesizers,
one piano, two blastophones, and one
elderly wind-powered organ. The bass
guitar was supposedly for my son
Steven, who’s studying it in his high
school music class, but I also find uses
for it in the jazz band I play with.

The way we learn music around my
place is to put something on the stereo
and then play along with it. Steven’s

48 ELECTRONICS Australia, October 1992

main source of inspiration has been a
CD of music from the sound track of the
film The Blues Brothers . He’s seen me
learning all the guitar parts for the songs,
and now he’s learnt them himself on
bass guitar.

The other day I pulled out another CD
Steven never knew I had, called
‘Genuine Houserockers Music II’. You
get the idea. Steven soon had the bass
guitar hooked up to its big amp, thunder¬
ing along with the stereo which was bel¬
lowing out such gems as ‘Mojo Boogie’.
Blues Brothers all over again, but a
whole new collection of tunes.

In the midst of all this my teenaged
daughter came home from school. You
know how in cartoons you sometimes
see captions with icicles dripping from
words? Well icicles were dripping from
her words, as she said “lovely music”,
and sulked off to her room. And this
wasn’t an isolated incident.

Steven and I have learned to enjoy our
music surreptitiously, while all female
members of the family are out We keep
one eye out the window overlooking the
driveway, so when Mum’s car pulls up
we can hit the ‘abort’ button on the CD
player. This short-circuits any insulting
comments about our tastes in music, and
its effect on female happiness.

Last Christmas my family gave me a
brand new, never been played, video of
the Blues Brothers film, knowing I liked
it so much. This particular video has a
stereo sound track, which seems to be
every bit as good in quality as the CD of
the same music. That means the sound
deserves to be played through the stereo
— LOUD — while watching the video.
Trouble is, every time I put the video on,
the female side of the family retires to
the far end of the house, dripping icicles
as they go.

This whole business raises an interest¬
ing scientific question: Is one’s taste in
music somehow linked to hormones?

The problem mentioned above works
both ways. The women in the family
have music they like — which are most¬

ly songs sung by women, interestingly
enough. Women like Barbara Streisand
and Bette Midler. Steven and I, on
the other hand, find recordings by these
artists less than pleasant, so the
women don’t usually play them while
we are around.

It’s not just in our family. When
singer Tom Jones comes to town, his
audience (I’m told) is almost entirely
women. I wouldn’t know by personal
experience, since I’ve always steered
clear of his concerts. His records are bad
enough. (Sorry Tom, but it’s just a mat¬
ter of taste.)

And then there’s James Blundell. He
played in Hobart the same night as our
Burglar’s Dog band was playing in the
usual pub, but that night our audience
was pretty short on women. Where were
they? Wrest Point Casino, lapping up
James Blundell.

Remember when girls used to faint at
the sight of the Beatles?

Even one song can be performed in
different ways that are poles apart in the
sex appeal stakes. Take for example, the
old classic ‘The Glory of Love’ - you
know the one: “You got to live a little,
love a little...” The very best version of
this song was recorded by a guy named
Big Bill Broonzy back in the 1930’s. At
the start of the song, before he started
the singing, he played it through several
times on the guitar in a nice bright
finger-picking style. I spent many long
hours studying his recording, learning to
play that guitar solo.

Then along came Bette Midler, with
the same song: “You got to liiiiivvvv uh
little...” — slow, dreary, horrible, the
song completely murdered. Yet this is
the version the women like.

What a miserable, bigoted, male
chauvinist diatribe this month, eh? But
there’s more to come.

From that same Bette Midler film
Beaches which gave us ‘The Gory of
Love* comes another song, something
about a hero (I have tried to blank it
from my mind). One afternoon I found

my daughter learning this dirge on the
piano (Oh no — Oh no!).

But there’s worse. On a trip to the su¬
permarket I heard it again, loud and
clear — coming from the Muzak! Right
there for all the lady shoppers, yeah!
Bette Midler records on the Musak, how
very appropriate.

No, I shouldn’t insult Muzak; after all
they gave me my first job in electronics,
indirectly (you can rest easy now,
ladies). Muzak is ‘background’ music
and background means ‘unobtrusive’ —
and unobtrusive music is generally dull
and boring, if you take any notice of it
That’s the point, you’re not supposed to
take notice of it. If it helps take the pain
out of the dentist’s drill, then that’s good.

When I was in high school every kid
had a part-time job to make some spend¬
ing money and help defray family ex¬
penses. There were lots of jobs back
then, of course.

My job was in the local FM
broadcast station, where I was allowed
to play classical records and announce
from time to time “This is KHFM, fine
music for Albuquerque through frequen¬
cy modulation”.

The station also held the local agency
for Muzak, and whoever was doing the
on-air shift was also required to keep an
eye on two gigantic ieel-to-reel tape
players that were the source of Muzak
for the whole city, distributed by a net¬
work of telephone lines. There wasn’t
much money for a kid working in the
studio, since your real payment was sup¬
posed to be the glory of broadcasting
your own voice on air. The big bucks
was in installations.

Every new Muzak subscriber had to
have his premises wired up with
speakers in the ceilings, speakers in the
walls, or headphones for the dentist’s
chair. This meant crawling through the
roofs and under the floors, through the
dark and spider webs, mixing it with the
rattlesnakes and tarantulas.

Qualified technicians were in charge
of such installations, but there was no
way they were going to crawl around
under buildings. The solution: hire a kid
to do it. In particular, a kid named Tom
Moffat, who was silly enough to do such
things just to raise some spending
money. I also learned from working at
that FM station that there’s good money
in climbing broadcasting towers, to paint
them or change light bulbs. That was a
pretty good earner over the years.

Just the other day, as I was putting a
BNC connector on the end of a cable, I
was reminded of the second job I had in
electronics. There was a government
contractor which was constructing a big

telemetry system for a missile test range.
The system was made up of a bank of
perhaps eight equipment racks, filled
with receivers, demodulators, and all the
other bits and pieces needed to gather
and record data.

I was hired as sort of a temporary
trainee-technician-flunkie-kid, to assist
the real technicians. Every signal line in
this telemetry system was of 50-ohm
coaxial cable; every cable had two
ends; and every end needed a BNC con¬
nector. It was my job to put on those
BNC connectors. I put on BNC connec¬
tors all morning, I had lunch, I put on
BNC connectors in the afternoon, and
then I went home. I dreamt of BNC con¬
nectors at night.

That was a miserable job. I thought I
was going to learn about electronics, but
instead I became a machine for putting
on BNC connectors...

Nowadays there are crimp-on BNC
connectors, which save the trouble of
manually stripping and preparing the
cable and then screwing the bits of the
connector together. But they are for mass
production: if you want to do one or two
BNC connectors you do them the old
way, like I did in my youth.

I still cringe from BNC connectors
today. During development of a weather
satellite receiving system, I discovered
that the connections feeding the antenna
coax into the preamplifier were not in
the best condition, and they were mess¬
ing up the system noise figure. A new
BNC connector was in order, and as I
installed it I felt every cramp and twinge
in my hands that I felt from the hundreds
of BNC’s I installed in my youth. Old
memories die hard!

Back to music for a moment: You may
remember the Moffat’s Madhouse
column from March, about old-time
mechanical musical instruments. It ap¬
pears there are a lot of people interested
in such things out there. That column
seems to have generated more mail than
all the other Madhouses put together.
One fellow sent me a catalog from a
place in the USA that sells recordings of
all kinds of interesting musical stuff, in¬
cluding my own Aeolean paper-roll
wind organ.

Another real prize came from a reader
who was a fellow admirer of that Robot
Orchestra in Sydney. It seems the Robot
Orchestra’s owner has produced a tape
to promote the machine for use at parties
and functions. The reader sent me a copy
of the tape.

A testament to the musical quality of
this tape is the fact that it is now on the
‘banned’ list at home, along with the
Blues Brothers and Genuine Houserock-

ers and all my noisy Zydeco records. In
other words, it’s great!

All that interest in mechanical music
and the availability of recordings makes
me wonder if there shouldn’t be more of
an outlet for this kind of stuff. Maybe I
should approach the ABC with a
proposal to do an occasional program
segment for them, for Radio National or
ABC-FM.

I’ll bet heaps of people would
listen to it But I don’t think many
would be women! ❖

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ELECTRONICS Australia, October 1992

THE SERVICEMAN

A collection of ‘not worth fixing’
items rescued from the rubbish tip

A steady trickle of correspondence has given us enough fresh and varied material to make this a
‘Contributor’s Month’. We have the intriguing story of a number of different items rescued from being
thrown on the rubbish tip, by a contributor who describes himself modestly as a ‘kitchen table
serviceman’. There’s also a tale of re-repairing a set that has been ‘fixed’ by a competitor — and
diplomatically explaining to the customer why this was necessary...

On top of the pile is a letter from K.D.,
of Taringa in Queensland. K.D. has ap¬
peared in these pages before, when he
chased a dozen faults around an old
Philips K9. He is back with another
Philips — this time a K11 — along with a
few other items whose problems had
threatened to get them junked.

He has called his story ‘...It’s Not Worth
Fixing!’, and this is how he tells it:

Ay an amateur serviceman, most of
the jobs I get are from friends. Over
the past few months I've had a spate of
jobs where the owners told me that “the
equipment isn't worth fixing'. In each
case the problem turned out to be some¬
thing quite simple.

The first item was literally saved from
the tip. I'd called in to visit a friend, and
saw his old Philips Kll television

amongst a load of rubbish on his trailer.
He said that it had recently failed totally'
and, thinking it not worth repairing, he
had bought a new set. Despite the age of
the set I knew that it had always given a
superb picture, so I asked him to dump it
at my house.

When I switched the set on, I found that
it wasn't as dead as my friend had
thought. The sound was normal, but the
picture was only a blurry blob. It took
only a second to realise that the focus had
failed; and about as long to replace a
faulty 5.6M resistor in the focus chain. In
less than five minutes, the set was again
delivering a first class picture!

I rang my friend and told him t hat
he could pick up his television — but
he wouldn't hear of it and insisted I
keep the set. I didn't refuse, and now use
the Kll as a 'loan' set when I have others
in for repair.

The next job was a large Sony stereo
radio-cassette featuring a solenoid-con¬
trolled tape transport, digital frequency
readout and clock, as well as facilities for
the connection of a turntable and an
auxilliary source. The unit had two faults:
it would destroy tapes, and intermittently
the sound would drop to a very low level,
with some distortion. The tape problem
was easily solved with a new pinch roller.

The sound problem was a little more
difficult. It affected both channels equally,
and was present irrespective of which
input was selected. I didn't have a copy of
the circuit, but chose to start my search at
the volume controls, as they were the most
identifiable part of the amplifier chain.

The signal level was reasonable here,
so the problem was probably in the power
amplifier. I wasn't too concerned with the
details of the circuit but, as the fault ef¬
fected both channels, I reasoned that it

must be in an area of the amplifier com¬
mon to both channels.

The unit is of an age that it uses mostly
discrete transistors, so I simply traced
through the signal path and whenever I
found two components the same (one for
each channel) I mentally checked them off
as not being the cause of the fault.

My search lead me to a resistor
which had no mate. It connected to two
other resistors, each of which connected
to the base of a transistor in the signal
path. Connecting the end of this unpaired
resistor to the earth rail gave me a work¬
ing amplifier. All I had to do now wasfind
out what this part of the system was sup¬
posed to do.

While the amplifier components were
all in one small area, the track from this
lone resistor meandered off across the
board. I followed it to a transistor, half
hidden behind a plastic moulding forming
part of the chassis.

The track from the base of this transis-

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READER INFO NO. 13

ELECTRONICS Australia, October 1992

tor disappeared behind the moulding.
Removing the large main circuit board
was out of the question, as it would in¬
volve disconnecting dozens of wires, and
stripping all the hardware from the chas¬
sis, so I resorted to connecting one
end of an ohmmeter to the track and
probing about the board until I found the
other end. It turned out to go to a small
switch which was part of the input selec¬
tor bank. A little experimentation showed
that the contacts of this switch closed
momentarily each time a different input
was selected.

I scratched my head for a while, then
realised that this system must briefly mute
the amplifier each time the source is
changed, and that the fault’ condition
represented the muted state. I didn't
bother to work out the details, but decided
to test the transistor first.

The transistor was faulty, but with it lo¬
cated behind the chassis, removing and
replacing it generated a certain amount
of swearing—and more than a little plas¬
tic melted onto the barrel of my soldering
iron. But with this done, the Sony per¬
formed perfectly.

The next visitor to my bench was a
Thorn 9007 television. It was completely
dead. Once again I didn’t have a copy of
the circuit, so I just had to ‘play it by ear’.

The most obvious thing to do was check
all the fuses, and I found F591 blown. I
followed the wires from this fuse to the
horizontal output stage. The output tran¬
sistor Q503 was OK, so I had to look fur¬
ther afield.

On this set, the horizontal and vertical
output transistors are mounted on a metal
assembly, with a small circuit board be¬
tween them. There are only a few com¬
ponents involved with the horizontal
output on this board, so I started there.

Murphy must have been on holidays,
because a lOOuF electrolytic capacitor
(C535) in the base circuit of the output
transistor was faulty. Another cheap and
quick job resulted in a further set saved
from an early retirement.

When I saw the condition of the next
job to arrive, though, I was almost
prepared to throw it straight into the bin.

I was asked to give an opinion on two
items, for a friend who works for a mining
company. The items in question were a
Sanyo portable colour television and a
Titan Betamax video recorder. Both had
been used in the South Australian desert
and were covered in — and full of—fine
red bulldust.

The television was functional, but the
centre of the screen was badly scratched
due to rubbing against something while
being transported. The damaged area
was about the size of my hand, and the

picture in this area was virtually un-
watchable. The company wasn’t prepared
to spend any real money on the repair, so
I had to devise a simple means of fixing
the surface of the picture tube.

As my 'real job’ is a research chemist, I
immediately thought of using a suitable
monomer to fill the scratches, then
polymerising it in place. (Hold on! This is
an electronics magazine and we’ll have
none of that sort of language here! —Ed.)
But the budget wouldn’t even stretch to
this, so in the end I dissolved some hard
colourless wax in hot toluene and applied
this solution to the screen.

The end result, after a lot of buffing,
was an acceptable picture — when
viewed from more than a couple of
metres. It wouldn’t be acceptable in a
domestic situation, but as the only source
of entertainment on a remote drill site it
will be more than adequate.

(One point that should be made here is
that scratches can seriously weaken the
bulb of the picture tube. If the scratches
are more than just superficial, the tube
should be discarded. — Ed.)

The video recorder was a different
proposition. The tapes that came with it
were so contaminated that you could
shake a dust storm out of them. The re¬
corder wasn’t in much better shape. As
well as the dust, it contained dead moths
and an assortment of small leaves and
seed pods. I imagined that the heads
and tape path would have been badly
damaged.

I spent about an hour cleaning it all
out, and with a clean tape it gave surpris-
ingly good results. Granted it wasn’t a
perfect picture, but the recorder has been
used at home for a couple of months
since, with only a single tape, and still

gives the same results. It never ceases to
amaze me how much abuse things like
VCRs can take, and still bounce back.

The last item was a five year old Teac
VHS video recorder which wouldn’t
rewind or fast forward. When either of
these functions was selected, the recorder
would display the appropriate symbol for
a few seconds, then switch itself off and
flash the ’tape’ symbol to indicate a fault.

With the bottom cover off I could tell
that the motor and belt were functional.
Without a manual I had to use a process
of elimination to work out what combina¬
tion of gears should turn for the fast wind¬
ing functions. It appeared that one gear
wasn’t toggling across properly, and a
gentle push here resulted in a soft click
from somewhere on the top of the deck.

After tins the fast winding functions
would work once only. If the motor was
stopped a further 'push and click’ cycle
was needed.

On the top of the deck I eventually
narrowed the problem to two nylon
levers, almost hidden at the front of the
deck. Both levers moved relative to the
chassis and to each other. The top one
had a spring-loaded catch, that was sup¬
posed to lock onto the end of the lower
one each time the transport came to a
stop. The latching action failed by just a
whisker to engage.

I removed, cleaned, and lubricated this
assembly, without any improvement.
After quite a lot of poking and prodding I
reached the conclusion that the problem
probably lay with the top lever. This
lever is pulled to the rest position by a
spring and the stop is formed by a
rubber collar around a metal finger
pressed from the chassis.

This rubber collar had deformed slight¬
ly, due to the constant pressure from the
lever. I simply rotated the collar by 180°,
and the problem was solved. I estimate
that the deformation of the rubber collar
amounted to less than a millimetre, but it
was enough to effectively prevent the
catch from working and so make the re¬
corder useless.

This fault took me about two hours to
solve. I doubt that anyone could have
done it much quicker, unless they had
seen the exact fault before. Who would
ever think that a liny rubber stop would
cause a problem like this?

Well, those are a few simple faults I’ve
encountered recently. I can’t help but
wonder, though, what would have hap¬
pened to these items if the owners hadn’t
known a ‘kitchen table serviceman such
as myself. I’m sure most of them would
never have been repaired, but consigned
to the local tip.

Thanks for those interesting items.

ELECTRONICS Australia, October 1992

THE SERVICEMAN

K.D. You might only be a ‘kitchen table
serviceman’, but you’ve uncovered at
least one unusual fault that will be of
value to a lot of us professionals. Don’t
disparage your efforts. There’s a place for
everyone who approaches the job in a
conscientious and workmanlike manner.

Repairing a repair

Now we come to a story from a fre¬
quent contributor. It’s from L.K., of
Daintree in far northern Queensland. I
usually look forward to L.K.’s next con¬
tribution, because of his wry sense of
humour and witty pen. This time, how¬
ever, he is quite serious and his pen writes
more in sorrow than wit. I’ll let him tell
the story in his own words:

In my opinion, one of the worst jobs a
serviceman can encounter is having to
correct a shoddy repair by another tech¬
nician. It's even worse when that other
technician is known to you—even though
he may be your opposition!

It is not just that person who is seen in a
poor light, but the trade as a whole which
is degraded in the eyes of the public.

The saga began when a woman brought
a Sanyo portable colour television to me,
explaining how she had been advised that
the picture tube was faulty. Wisely, I think,

she just wanted a second opinion before
outlaying the cost of a replacement. It was
a reasonably late model set, fitted with an
83P chassis.

“Could you do it today?” she asked.
“Yes, I can", I replied, believing that
I had a brief, straightforward task
ahead of me.

Later, I slipped the back off, lined the
set up on the bench, and switched on. The
picture tube sprang to life immediately —
the filament glowing white hot, like an in¬
candescent bulb. My initial thought was
that it had shorted to itself about halfway
along its length, which would have con¬
firmed the other technician's diagnosis.
But this job was not to be so easy.

I switched the set off and was about to
measure the heater resistance when I
noticed two wires coming from those
pins on the tube socket — and then
looped several times around the line out¬
put transformer's core. Definitely not a
Sanyo original!

Not knowing the history of the set, my
thoughts changed direction. It now
seemed as though the tube had developed
a low emission problem, and that this was
someone's brute force method of milking
a little more life from it. (By raising the
filament voltage, one also raises the
cathode temperature — thus releasing
more of the available electrons.) Still, my
task was to prove it—or cure it.

I removed one loop of wire from the
core as a precaution, because the way it
was glowing, I was afraid that the heater
might fail completely while it was in my
shop. When next I applied power, things
looked a little safer and nearer normal.
The picture itself came up dark, but
without any sign of the 'pasty' look so
common when a tube is showing the signs
of age. I tried disconnecting the antenna,
but the resultant snow was too dark for
me to draw any conclusions.

It was, in fact, just like the bright¬
ness control had been backed off. But a
quick check proved that it, and the sub¬
brightness control, were turned all the
way up. For the first time, I became suspi¬
cious that this set might have some other
subtle fault.

A voltage check around the tube's base
board didn't reveal anything abnormal. I
followed this with an investigation of the
two brightness controls, but again I drew
a blank.

But I still wasn't convinced, and fired
up the CRO to observe the DC level of the
back porch. I hoped this would reveal,
quickly, if I had some sort of pedestalfault
present. The measurement came up at
90V, which in my experience was getting
on for 20V too high for a tube of that kind.
The tube was simply being biased off!

Another careful scan of the schematic
brought me back to the brightness cir¬
cuitry and IC201 (which seemed to do
just about everything but boil the kettle!)

Having already looked at both poten¬
tiometers, I eyed the IC suspiciously —
that is, until I noticed it had recently been
changed. Ay a result, I felt that not only
was a malfunction in that department un¬
likely, but also that I was following some¬
one else around the trail.

Turning again to the brightness area,
the measured voltage on pin 46 of IC201
was only TV at its maximum — a mite
short of the suggested 8.4V. Yet the 18k
resistor R222 was spot on, and C226 was
not leaking.

I began pondering the ramifications of
a shorted D226, when I realised what
should have been obvious. If R234, an
82k resistor to the 130V rail, had gone
high, it would allow the diode to conduct
— thus shunting the brightness com¬
ponents with R230, an 8.2k to earth.

Sure enough, that is just what I found.
And replacing R234, refitting the original
heater wiring to the tube base and reset¬
ting the sub-brightness control brought
the set back to normal operation, with no
signs of any adverse effects from its
maltreatment.

Just the same, I still wonder how much
the life of the tube has been shortened as
a consequence.

Contributor L.K. was asked to provide a ‘second opinion ' on a Sanyo portable
colour TV which supposedly had a faulty picture tube. In fact, it turned out to have
a hard to find fault in a relatively low cost component, in this part of the circuit

52 ELECTRONICS Australia, October 1992

Looking back along the path, I presume
that my predecessor had worked to much
the same routine as I had, until he
changed the IC. When this proved unhelp¬
ful, he must have felt convinced that a
tube fault existed, and so boosted the fila¬
ment in a ‘nothing to lose ' effort at
squeezing out the last few hours from it.

To me, the most difficult part of this job
was not the diagnosis and repair, but the
embarrassment of having to explain
diplomatically to the customer that a mis¬
take had been made, while trying not to
downgrade the individual concerned or
the trade as a whole. It is not a job I
would leave to the counter staff, though
Til admit the temptation is often there.

I can quite understand your concern,
L.K. I imagine that most of us have
had, at some time or another, to re¬
repair (if that term is permissible) the
shoddy work of others. And as you say,

trying to explain it without making the
whole industry look disreputable is not an
easy task.

3 times 2 = 7?

Now on to happier things — although
our next contributor would not have
thought so at 3am on a cold winter’s
morning. The story comes from Mr A.F.,
of Balwyn in Victoria, and comes in the
form of a personal letter.

It seems that in the event he solved the
problem without getting out of bed! Oh,
how I wish I had lesser mortals to do the
hard yakka for me, while I lay back doing
the thinking, in comfort.

Enough dreaming, though. Here’s
A.F.’s story:

The story in the December issue about
the fault in a broadcast transmitter
reminded me of a problem I had around
1960. At that time I was responsible for
all transmitters in Victoria carrying the
ABC programmes — the PMG's Depart¬
ment provided the transmitters and all
technical staff, and the ABC provided the
studio buildings and programme staff.

About 3.00am I was woken by a frantic
call — they were rebuilding the aerial
coupling unit and needed a 6nF
capacitor. They had three 2nF capacitors
which each measured within a few per¬
cent of 2nF, but when they were con¬
nected in parallel the combination
measured 7nF.

They had separated and measured the
capacitors a number of times, then con¬
nected them in parallel again. Each time
they were individually 2nF, but each time
the three combined read 7nF. Where was
the extra InF coming from? Could I
please come out and help immediately?

It was a good hour's drive to the trans¬

mitter. They had been working on the
problem since midnight, and were frozen
through from standing about in the middle
of a paddock in an icy wind. They were
too cold to think clearly any more. But the
coupling unit had to be ready to use by
6.00am, when the station opened. Some
quick thinking was needed.

Before you try to work it out, I had bet¬
ter give you some more background infor¬
mation. The aerial was an ‘inverted
Delta’ type. It consisted of three 30-metre
wooden poles, spaced about 100 metres
apart on the corners of an equilateral tri¬
angle. The aerial consisted of a wire
strung between each pole , with a
downlead from each apex to a central
feed point just above the ground.

The ‘wires were actually a group of
wires, arranged around circular
spreaders so that they formed a hol¬
low tube about 150mm in diameter.
The whole aerial looked like a three-sided
pyramid standing on its point — hence
the name ‘Delta .

The aerial had a high capacity to
ground and was electrically short —
about UlO of a wavelength—so that the
input impedance was about 45 ohms. The
coupling unit was being upgraded for use
with a lOkW transmitter, so the input cur¬
rent to the aerial would be about 45 amps.

Now, the capacitors used for this sort of
application are not exactly small. They
are housed in a steel box, they are oil-
filled to increase their voltage rating and
to help with cooling. Finally, the leads are
brought out on two large, ceramic in¬
sulators. I

t's a long time ago, but memory sug¬
gests that each capacitor was about
500mm long, 300mm wide and about
250mm high. The three capacitors were

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READER INFO NO. 14

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LOOKING FOR SEMI S?

We stock both Japanese & European
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Transistors-

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READER INFO NO. 15

SERVICE

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THE SERVICEMAN

joined in parallel with two pieces of
37mm x 3mm copper busbar, about 800
or 900mm long.

There wasn't really time to drive out to
the transmitter site. Anyway, T ve done my
share of freezing alongside coupling units
and it's much easier to think clearly in a
nice warm bed, even at 3.00am. So it be¬
came a question and answer session:

Ql: How was the capacitance
measured?

Al: It was measured at 620kHz (3AR)
using an RF bridge. It didn't matter
which end of the busbar it was con¬
nected to — the result was always 7nF.
Q2: What value is measured if the
bridge is connected across the centre
capacitor?

A2: (After several minutes of measuring
and re-checking) About 65nF.

So there was the clue. At 620kHz, a 6nF
capacitor has a reactance of around 43
ohms. 7nF has a reactance of about 37
ohms, a difference of about 6 ohms.

Where is all this leading? Well, at
620kHz a 15 uH inductor has a reactance
of about 6 ohms. Then remembering that
a capacitor has a negative reactance and
an inductor a positive reactance, then
putting a 15uH inductor in series with a
6nF capacitor will make it appear to
have a capacitance of 7nF when
measured at 620kHz.

It's not hard to imagine that the leads
joining up the three capacitors could
easily have an inductance of around 1 to
2uH. And the 65nF approx measured
across the centre capacitor — I'll let you
work that one out!

The moral of the story is that you can¬
not afford to forget the effects of circuit
inductance, as I said in a recent letter to
Peter Philips.

Now to another matter. I was browsing
through some of my earliest copies of
'Radio and Hobbies’ over the Christmas
holidays, and came across a couple of

Fault of the Month

Kreisler 59-03 CTV

SYMPTOM: The sides of the picture are
bowed inwards. The East-West pin¬
cushion adjustment and width controls
have not effect. Top and bottom lines are
quite straight.

CURE: The core of L792 is either missing
or misplaced. The inductance of this coil
controls the line frequency current to the
width modulator.

This information is supplied by courtesy of
the Tasmanian Branch of The Electronics
Technicians’ Institute of Australia (TETIA).
Contributions should be sent to J. Lawler,
16 Adina Street, Geilston Bay, Tasmania
7015.

items that may interest you. There's an
editorial on licensing servicemen, and an
article on repairing volume controls. The
latter brought back to me memories of
trying to chose the 'right' grade of
graphite pencil to repair a worn track.
Try the 'Hamlet Approach’: 2B or not 2B.

You might enjoy reading the attached
photocopies when you get a few moments
to relax — just to remind you how easy
things are these days.

With my very best wishes for the long
and continued success of your column.
It's the first thing I read each issue (after
the Index, that is).

Thanks for your letter A.F., and for the
kind wishes expressed in the last para¬
graph. It’s nice to know that people ap¬
preciate our humble efforts.

I’ve chosen to use the transmitter story
as it carries a useful reminder that an ap¬
plication of basic theory can sometimes
be of benefit. Not that those poor in¬
dividuals in the paddock would have ap¬
preciated the niceties of positive and
negative reactance at 3am in mid-winter!

Next, your reference to the old Radio
and Hobbies magazines and one of the
wartime editorials was quite timely.
There is some strong feeling in the trade
that servicemen should be licensed, and
the old editorial reminds us that the in¬
dustry was not always as free and easy
as it is today.

The old licensing system was a wartime
necessity, but it guaranteed to the public
that servicemen were qualified and ac¬
countable. Nobody wanted to lose the
licence that provided his living.

The same applies today and some kind
of licensing system would give the public
protection over shoddy workmanship and
un-ethical practices. Unfortunately, it
won’t stop careless work, but it would
provide an avenue for compensation.

And finally, your reference to repairing
old volume controls. It was a real trip
down memory lane. I well remember the
pencil problem and the fact that the only
grade available during and just after the
war was the old HB (Hard and Black!).

These were useless for repairing the
carbon tracks on old potentiometers,
though I do remember having some suc¬
cess by grinding the pencil onto fine
sandpaper, then transferring the black
powder to the track and binding it with a
thin solution of bone glue.

Who would bother these days — as¬
suming one could even get inside the
miniature and sub-miniature pots used in
modem equipment? Hasn’t life changed?

Well, that’s all for this month. I
don’t know what next month will
bring, but you can rest assured that it
will be interesting. ❖

READER INFO NO. 16

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READER INFO NO. 17

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READER INFO NO. 19

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RITRON

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80386SX 25M CPU
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SERIAL PARALLEL GAMES PORTS
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<M /IQQ TAX WITH 200 MEG DRIVE
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ROD IRVING ELECTRONICS

Basic Electronics - Part 16

The Operational Amplifier

The first 1C to appear in this series was the 555 timer, described in part 15. In this part, we describe
another 1C, called the operational amplifier. As you’ll see, these are amazing devices that are
capable of performing a wide range of useful functions.

by PETER PHILLIPS

Years ago there were two types of
computers, called the analog computer
and the digital computer. These days,
virtually all computers are digital, and
the analog computer has been largely
superseded.

The analog computer was a relatively
simple device and consisted of a number
of high gain amplifiers, called opera -
tional amplifiers. The idea was to con¬
nect the various amplifiers so they could
solve a mathematical expression and
thereby perform an operation.

A classic example is to use an analog
computer to design the suspension
system of a car. Although the equation
for the system is complex (called a
second order differential equation),
with appropriate connections, a string
of op amps can be connected to solve
the equation.

In this case, a bump in the road would
be a pulse input from a variable voltage
source, adjusted for various sizes of
bumps. The output is a waveform on
an oscilloscope.

Other adjustments in the circuit would
include spring stiffness, the viscosity of
the fluid in the shock absorbers and so
on. Once connected, the designer can

then fine tune all the components so that
the bounce resulting from a bump gives
the best response for the system, as dis¬
played on the oscilloscope.

Although such an operation is beyond
the scope of this series, this example il¬
lustrates the versatility of the opera¬
tional amplifier. In fact, because the op
amp is such a useful device, a large
number of books have been written
about these devices.

We’ll keep things more basic and
describe a few of the more commonly
used applications. But if you want to
take the topic further, be assured there is
no shortage of literature on the subject

The op amp

As we’ve already said, an op amp is
an amplifier with a very high voltage
gain. The schematic symbol of the op
amp is shown in Fig. 1(a), which as you
can see shows one output and two input
terminals. The power supply is con¬
nected to the other two terminals.

The signal inputs are known as the in¬
verting input, shown with the *-’ sign,
and the non-inverting input, indicated
with the V sign.

An important point to keep in mind is

that the signal input to the amplifier is
applied between both input terminals.
The input signal voltage to the op amp is
therefore the voltage difference between
these two terminals, shown as vd in
Fig. 1(b). This voltage is often called the
differential input, as the op amp
amplifies the voltage difference between
these terminals.

For example, if both inputs are at +1V,
there is no difference and the output will
be zero. However, if one terminal is at
+1V and the other is slightly more posi¬
tive, a voltage difference is present be¬
tween the inputs and an output voltage
will result.

The power supply for an op amp is
slightly different to most ICs, and
usually requires a dual-polarity supp¬
ly, shown by the two batteries in
Fig. 1(b). This supply has three ter¬
minals: positive, negative and the com¬
mon (or earth) terminal.

This type of supply is necessary to
allow the output to go either positive or
negative, depending on the polarity of
the input voltage. While it is possible to
operate an op amp from a single rail
supply and to use a coupling capacitor at
the output as in a conventional transistor

(b)

+ve

+ve <

-ve <-

Fig. 1: The symbol of the op amp is shown in (a). The dual-polarity power supply shown in (b) illustrates the usual type
of supply required by an op amp. The input signal is applied between both inputs and the output is between the output
terminal and ground.

ELECTRONICS Australia, October 1992

amplifier, most op amp ICs require a
dual-polarity supply for best operation.

Op amp characteristics

It is useful to consider the op amp as
an ideal amplifier, as in most cases the
actual characteristics are not far
removed from the ideal. The first of
these is the voltage gain.

An ideal op amp is assumed to have a
voltage gain of infinity. This means that
an output will occur for a differential
input of zero. In practical terms, this
means the voltage difference at the input
terminals is low enough to assume it is
virtually zero.

The usual voltage gain of an op amp is
around 200,000, meaning a differential
input of only lOuV gives an output of
2V. This is a very useful point to remem¬
ber, as it means we can often (though not
always) assume that the voltages at both
input terminals of the op amp are equal,
as in reality they often differ by a only a
few microvolts.

The next characteristic is input resis¬
tance. Ideally, this should be infinitely
high (or open circuit). If the input resis¬
tance is ideal, no current flows into the
input terminals. In practice, the input
resistance (resistance between the input
terminals) is generally between about
1M ohms and over 100M ohms, depend¬
ing on the type of op amp. Therefore,
while a small input signal current may
flow, it is small enough to be ignored.

Then comes output resistance. The
ideal value is zero, and in most practical
cases this value is again small enough to
be ignored.

Of course, this doesn’t mean the op
amp can supply unlimited current to a
load, as it would quickly bum out. Most
op amps have some form of internal cur¬
rent limiting to prevent them burning out

if the output is shorted to ground, but
under normal operating conditions, the
output resistance is low enough to as¬
sume it is zero.

The next characteristic is frequency
response (or bandwidth). This is a rather
strange characteristic as the ideal
bandwidth is infinity. That is, the ideal
amplifier can amplify frequencies from
0Hz (DC) to frequencies above that of
light. In fact, practical op amps often
have a rather low bandwidth — often as
low as 10Hz. However, given suitable
external circuitry, the useful response
can be extended to over 1MHz, which
for most applications is high enough to
regard as ideal.

Another interesting characteristic is
the assumption that a zero output will
result for a zero differential input. In
practice, if the differential input voltage
is zero, a small DC output voltage will
often result.

This is called offset and can be can¬
celled or compensated with external cir¬
cuitry. Most op amps have some facility
to allow adjustment for obtaining zero
offset, which becomes important when a
DC signal needs to be amplified.

One point we need to make is that
many op amps have a small DC bias
current flowing through both input
terminals. This current is similar to the
base current required in a transistor,
and is produced by the internal circuit of
the op amp. The main consideration is
that a DC path to ground for each input
terminal needs to be provided by the ex¬
ternal circuit

Ideally, the DC resistance to ground
from each input terminal should be the
same. In some cases, the DC bias current
will flow to ground through the signal
source, meaning it needs to be DC
coupled to the op amp. All the circuits

shown in this part have the required DC
paths, although for simplicity, their
resistance has not been made equal.

There are other characteristics as¬
sociated with an op amp, but we’ll
leave these for now and explain them
as the need arises. The best way to ex¬
plain how all this fits together is to
describe how the op amp can be used as
a basic amplifier.

Inverting amp

An op amp on its own has too high a
voltage gain to be useful, in a lot of cir¬
cuits. As we’ve already explained, a few
microvolts at the input terminals of the
op amp will produce several volts at the
output To reduce the voltage gain to a
useful value, negative feedback has to be
applied to the op amp.

You might remember we discussed
negative feedback when the transistor
amplifier was described. This type of
feedback is a connection from the
output back to the input, arranged so
the output voltage subtracts from the
input voltage. The amount of feedback is
determined by the feedback circuit, and
is often some sort of resistive network
that supplies a fraction of the output
back to the input.

The amplifier circuit we are going to
describe is shown in Fig.2, and is called
an inverting amplifier, for reasons that
will become clear. As you can see, the
circuit is quite simple, consisting of the
op amp and two resistors. The power
supply connections aren’t shown to
make the diagram easier to read, and the
power supply connections of Fig. 1(b)
would normally be used.

The feedback is provided by both
resistors, in which resistor Rf connects
the output back to the inverting input,
with resistor R1 acting with Rf to reduce

Rf 10k

Av = (-)| 1 = ( - ) - ! ^=- 1 0
R i lk

Fig.2: The basic inverting ampiifier is shown here. The (+)
input is connected to ground, and the input signal is applied
between ground and to the op amp via R1.

Fig.3: In this diagram, a current of 1mA flows in R1 and Rf
due to the 1Vinput voltage. The output voltage of the op amp
will be a value that therefore causes 1mA in Rf.

ELECTRONICS Australia, October 1992

Fig.5(right): The analysis of the non-inverting amplifier is shown here, in which a current of 1mA flows int both Rl< and Rf.
The differential input voltage will be zero, as the voltage at both input terminals is the same. As the equation shows, the
gain for this circuit is also determined by the external resistors. This circuit has a high input resistance.

the amount of feedback. To show
how this circuit works, we can use
Ohm’s law.

In Fig.3, values have been included,
with an input voltage of IV DC
applied between R1 and ground. Be¬
cause the differential input across the
input terminals of the op amp can be as¬
sumed to be zero, the voltage at the (-)
input of the op amp will equal the volt¬
age at the (+) input. That is, the voltage
at the (-) input is OV.

Because one end of R1 is at +1V (the
input side) and the other is OV, the volt¬
age across the resistor is IV. By Ohm’s
law, this will cause a current of 1mA to
flow in Rl. However, because the input
resistance of the op amp is very high
(ideally an open-circuit), the current in
Rl cannot flow into the op amp, and
therefore needs to flow in Rf.

For a current to flow in Rf, a voltage
drop must be present, which by Ohm’s
law must be 10V, with positive on the
left and negative on the right (at the out¬
put terminal of the op amp). Because the
left side of Rf is at OV, as we’ve seen, the
output of the op amp must be -10V.
Notice how the current in Rf flows into
the output terminal of the op amp.

By using Ohm’s law it is relatively
easy to show that the voltage gain
(Vout/Vin) of the circuit equals Rf/Rl.
The proof doesn’t matter, but the equa¬
tion (shown also in Fig.3) is important.
What this shows is that the gain of the
circuit is determined entirely by the
resistors. In fact, many op amp circuits
can be analysed this way, and some quite
complex circuits can be reduced to noth¬
ing more than Ohm’s law.

In practice, if you built this circuit,

you would find that the voltage gain
would be very close to 10. To change the
gain, you simply change the values of
either Rl or Rf. For example, if Rf was
changed to 100k, the gain would be 100.

Another point to note is that the
polarity of the output is the opposite to
the input. That is, for a positive input,
the output is negative. This is why the
circuit is called an inverting amplifier, as
the output has an inverted (or opposite)
polarity. If an AC signal was connected
to the input, the output would be 180°
out of phase with the input The gain is
still 10, and if the input was lVp-p, the
output would be -lOVp-p. The minus
sign refers to the phase inversion.

The next point is the input resistance
of the circuit. We said before that the
input resistance of an op amp is (ideally)
infinite, but this is not true for the whole

the output directly to the (-) input. The
gain of the circuit is unity, and the input
resistance is equal to the input
resistance of the op amp.

circuit. In fact, because the input voltage
is applied across Rl (as the other end of
Rl is at 0V), the input resistance of the
circuit equals Rl.

In some cases, such a low input resis¬
tance may not suit the application, and
another circuit configuration,
called the non-inverting amplifier
might be required.

Non-inverting amp

The circuit of the non-inverting
amplifier is shown in Fig.4. In this cir¬
cuit, the input voltage is connected
directly between the non-inverting
input and ground. The feedback net¬
work is still needed, this time with Rl
connected to ground.

However, because the input resistance
of the op amp is (ideally) an open-cir¬
cuit, the input resistance seen by the sig¬
nal is very high, and equals the actual
input resistance of the op amp. But this
time, the gain of the circuit is slightly
higher than for the inverting amplifier,
assuming the same value resistors.

In Fig.5, the values are included, again
with lk for Rl, 10k for Rf and a +1V
input. Because the differential voltage
between the op amp input terminals is
zero, the voltage at the (-)input will
equal the input voltage.

Therefore, because Rl is connected to
ground, it will have a voltage across it of
+1V, again causing a current of 1mA.
This current comes from Rf, supplied by
the output of the op amp.

As before, because the current in Rf is
1mA, there has to be a voltage drop
across Rf of 10V. However, as the left
side of Rf is at +1V, the other end needs
to be at 11V to give the 10V drop.

ELECTRONICS Australia, October 1992

Fig.7: The operation of the comparator is shown here. In (a), the (-) input is positive compared to the (+) input, giving an
output that is maximum negative. The opposite condition is shown in (b).

Therefore the output voltage of the op
amp is +11V, which is IV higher than
the previous circuit
The equation to determine the voltage
gain (Vout/Vin) of the non-inverting
amplifier equals (Rf/Rl) + 1, which can
also be proved with Ohm’s law. To
reduce the gain of the circuit in Fig.5 to

10, Rf could be reduced to 9k, or R1
could be increased to 1.1k. So again, the
voltage gain of the circuit is determined
entirely by the external resistors. But
this time, the input resistance of the cir¬
cuit is very high, being equal to the input
resistance of die op amp.

Notice also that here the polarity of

Flg.8: The comparator can be used In a control circuit, such as that shown in (a).
The relay, driven by the op amp, switches the heater element, and a thermocouple
senses the temperature. The action of the circuit Is shown In (b).

the output is the same as the input, hence
the term non-inverting amplifier. A
popular use for this circuit configuration
is as a non-inverting buffer.

In some applications, it is necessary to
connect a buffer stage between the input
and the rest of the circuit to ensure the
input source is not loaded by the circuit.
This might apply when the signal source
has a high output resistance, such as
some types of microphones, record
player pick-ups and so on.

A buffer stage using an op amp is
shown in Fig.6, in which the output is
directly connected to the (-) input. In this
circuit, because the voltage at the (-)
input will equal that at the (+) input, the
output voltage equals the input voltage.
In other words, the circuit has a very
high input resistance and also a voltage
gain of unity.

Also, the polarity of the output
will be the same as the input This is
similar to the emitter follower circuit
described in previous parts of this series,
and for this reason it’s sometimes called
a voltage follower .

The comparator

The circuits described so far all use
negative feedback to reduce the gain of
the circuit. The operation of circuits with
negative feedback can be analysed on
the assumption that the negative feed¬
back keeps the differential input volt¬
age at zero. However, there are times
when the full gain of the op amp is re¬
quired, and negative feedback is there¬
fore not used. One very common circuit
that doesn’t use negative feedback is
the comparator.

A comparator is a circuit that has only
two possible output voltages: maximum
positive and maximum negative, with a
value virtually equal to the supply volt¬
age. The polarity of the output voltage
will depend on the polarity of the dif-

ELECTRONICS Australia, October 1992

BASIC ELECTRONICS - 16

ferential input voltage, which is best ex¬
plained by Fig.7.

As shown in Fig.7(a) when the (-)
input is more positive than the (+) input,
the output is negative. Put another way,
a negative output results if the (+) input
is negative compared to the (-) input.

In Fig.7(b), the (+) input is positive
compared to the (-) input, giving a posi¬
tive output. Obviously, we can also say
that a positive output occurs if the (+)
input is positive compared to the (-)
input. A point to notice is that the dif¬
ferential input to the op amp is no longer
zero as it was for the amplifier circuits.

The reason is there is no connection
from the output back to the (-) input to
allow the amplifier to make the voltage
at the (-) input equal to that at the
(+) input.

Applications

The comparator is therefore (in
theory) the simplest circuit of all, as it
has no external components. It has many
uses in electronics, and is often part of
the interface between an analog circuit
and a digital circuit

A typical use of a comparator might be

to control the temperature of a heater. In
this example, shown in Fig.8(a), the
temperature is set by the voltage applied
to the (+) input.

The output of the op amp is connected
to a relay, which is switched on when the
output of the comparator is maximum
positive. Otherwise, the relay is off as
the diode prevents the negative output
voltage of the op amp from operating the
relay. The relay is used to switch power
to the heater element.

A thermocouple senses the tempera¬
ture, and is connected between the (-)
input and ground. As the temperature
rises, the output voltage of the ther¬
mocouple increases as in Fig.8(b).

When the thermocouple voltage ex¬
ceeds the voltage at the (+) input, the op
amp output swings negative, turning off
the relay. When the temperature cools,
the thermocouple voltage falls, allowing
the op amp to turn on the relay (and the
heater element).

Although the comparator seems to be
a simple circuit, it requires careful
design of the PCB layout to prevent
noise at the inputs from affecting the
operation. Also, the switching action at

the output can generate spikes in the
power supply, causing interaction with
other parts of the circuit.

A basic op amp can be used as a com¬
parator, but in most cases, ICs specifi¬
cally designed to perform the
comparator function are preferred.
These ICs can usually operate from a
single rail supply, and feature fast
switching at the output.

But what happens if both inputs of
a comparator are at the same volt¬
age? When this happens, the output
of the comparator becomes rather
unstable, as noise at the inputs will
cause the output to oscillate between
maximum positive and maximum
negative.

To prevent this, positive feedback can
be applied — giving a circuit called a
Schmitt trigger. This and other applica¬
tions will be described in the next part,
including some you might like to con¬
struct and experiment with.

We’ll also describe some more charac¬
teristics of the op amp and explain the
differences between the various types of
op amps.

(To be continued) ♦

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Every little one of them displaying that
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relays that switch loads up to 30 amps.

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sure every little thing is taken care of.

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Components

Little things make a big difference.

Phone (03) 420 7111 or fax us on (03) 420 7275 for more details. Ban SiE 0105

ELECTRONICS Australia, October 1992

READER INFO NO. 20

A Basic Guide to Colour

TV & VCRs

Two very popular series of articles, published in
Electronics Australia in the late 1980's, have now been
combined into a separate publication. Students, the
home handyman, even the serviceman, will find that the
latest publication from Electronics Australia gives a wide
and comprehensive insight into the electronics involved
in colour television and video cassette recording.

The author, David Botto, is a television, video and
electronics service engineer with many years of 'on-the-
bench' experience. He's also designed, constructed and
maintained a wide range of test instruments. Davids
wealth of exerpience and vast knowledge of colour
television and VCR's have been put together to give you
the facts, figures and basic knowledge you need, to un¬
derstand just how these entertainment machines work.

Available now from your local newagent or by mail
order. Price in Australia is $4.95, with an extra charge of
$2 for post and packaging, when ordered by mail, from -

The Book Shop,

Federal Publishing Company,

P.O. Box 199,

Alexandria, NSW. 2015

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... the choice is crystal clear when you

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READER INFO NO. 10

READER INFO NO. 11

READER INFO NO. 4

Construction project:

Flexible loudspeaker
protection circuit

Dubbed the ‘Protector’, this small module will save your expensive loudspeakers from damage due
to an amplifier fault or destructive drive signals. It includes an ‘intelligent’ de-thump circuit, and can
be either built into an existing amplifier or housed in its own enclosure as a free-standing unit.

by ROB EVANS

It’s safe to say that if you are running a
set of hifi or PA loudspeakers from an
amplifier which doesn’t feature
loudspeaker protection, then you’re
taking quite a risk. To put it simply, the
reason behind this danger is really the
limited power handling of the com¬
ponents inside the speaker box, which
are designed to handle AC signals at
audio frequencies.

If you take a two-way hifi loudspeaker
which has a nominal power handling of
say 150W for example, then it would be
reasonable to drive these speakers with a
similarly powered amplifier — so
theoretically, your speakers are not in
danger. If this amp is of a contemporary
DC-coupled design and develops a fault

however, chances are that the output will
‘latch up’ to one of its internal power
supply rails. The full DC supply rail
voltage — which would be around plus
or minus 50V for a 150W amplifier — is
therefore applied directly to your hap¬
less speakers.

Since a typical 8-ohm loudspeaker
will have a DC resistance of about six
ohms, a 50V source will cause at least
eight amps to flow through the bass
driver’s voice coil in a continuous man¬
ner. Not surprisingly, the 150W driver
suffers a gruesome death as it attempts
to handle the resulting 400W of dissipa¬
tion. There will be smoke, possibly fire,
and very likely a few expletives...

While you can take some small com¬

fort in the fact that the tweeter will sur¬
vive the carnage — since the crossover
network will invariably block DC vol¬
tages with its series-connected filter
capacitor(s) — don’t relax yet. There is
another fate waiting for this relatively
fragile device.

For a tweeter to handle high-frequen¬
cies with a reasonable response time, the
cone/dome and voice coil assembly
must be of a very light construction so
that it can move rapidly. While this in
turn means that the voice coil can only
dissipate quite limited amounts of
power, the nature of recorded music
means that there is only a small amount
of high-frequency energy which needs to
be reproduced by the tweeter, for a

ELECTRONICS Australia, October 1992

A shot of the completed Protector , in its prototype form. In this case the unit has been configured to suit a high-powered
amplifier (200W into eight ohms) — note that the components for Power Supply 3 have been fittedso that the circuit can
be installed inside the amp and powered from its positive supply rail.

balanced overall sound. And of course,
the crossover network ensures that the
much larger low-frequency energy is not
passed to the tweeter.

So under normal circumstances, a
tweeter with a raw power rating of say
20W will be more than happy in a 150W
loudspeaker system. But as we all know,
things have the unfortunate habit of not
remaining ‘normal’...

Imagine for a moment that the
driving amplifier has become unstable
at high frequencies, and begins to
oscillate at some supersonic pitch —
which of course, even the most refined
human ears won’t pick up. In this case,
the energy is dutifully passed to the
tweeter by the crossover network, where
the voice coil attempts to both respond
to the frequency, and dissipate the result¬
ing heat build-up.

It really has no hope on either
count, since both the frequency and the
power level are just loo high; the amp
will invariably oscillate at full power,
and at frequencies of up to a few
megahertz. So, as the old rhyme goes:
pop goes the tweeter...

Unfortunately, a tweeter can also be
dispatched in short order when an
amplifier is driven into severe clipping.
This is due to the large amount of high-

frequency energy which is generated
when the amp’s output is driven into the
‘end-stops’ (the supply rails), where the
drive signal takes on a harmonic content
approaching that of a square-wave. In
practice, this energy would exceed the
tweeter’s 20W rating, and overheat the
voice coil after a reasonably short period
of sustained amplifier overload.

While you may consider the chances
of your amplifier running into sus¬
tained distortion to be quite remote,
since of course the audible result is ex¬
tremely obvious, many a careful listener
has been tricked by the large dynamic
range produced by a compact disc
player, for example. All it takes is to
set the amplifier’s volume too high
during (say) a quiet section at the begin¬
ning of the disc, then unwittingly pop
out of the room for a moment just as
the full recorded level kicks in —
thereby driving your amp into an un¬
checked overload.

A less convoluted scenario is the in¬
famous party, where the volume of the
music simply gets louder as the night
wears on. As celebrations reach a
hedonistic peak, nobody (except the
neighbours) seems to notice or care that
the music has become grossly distorted
— thanks to each passer-by giving the

volume knob another tweak. Needless
to say, the host (or parents of) will
find their speakers sounding decidedly
‘flat’ the next day, thanks to a set of ex¬
pired tweeters.

As an aside, we know of one festive
situation where a three-way speaker sys¬
tem first lost its tweeters, then the mid¬
range drivers (“What’s wrong with the
sound? Never mind, turn it up”), and
then the electrolytic capacitors in the
crossover network — which exploded
inside the enclosure, as their voltage
rating was exceeded.

Finally, the amplifier overheated,
blew its output transistors and
delivered its DC supply rail to what
was left of the speakers. Needless to say,
this in turn took out the bass drivers
(“What happened to the music, and
what’s that smell?”). Then, fortunately,
the amp’s fuses gave out before the
driver’s coil former caught fire. After a
brief moment of silence as those present
observed the smouldering remains, a
search was quickly mounted for a port¬
able tape player...

That’s a hand-on-heart true story, by
the way.

Likely or unlikely, the above situa¬
tions (except perhaps the last) are cer¬
tainly on the cards, and can be very

ELECTRONICS Australia, October 1992

Flexible loudspeaker protection circuit

Fig.1: The Protector’s main schematic diagram. The upper section of the circuit controls the action of the speaker switching
relay RLA, while the circuitry based around IC1 in the lower half of the diagram senses DC (ICIa/b) and high-frequency
(ICIc/d) error conditions.

expensive to rectify. It’s on these
grounds that our new speaker protector
offers particularly cheap insurance
against loudspeaker damage, since it
offers protection against both
dangerous DC levels, and excessive
drive at high frequencies.

As a bonus, the Protector also has
turn-on and turn-off muting, which is
rather more sophisticated than the
simple de-thump circuits of past designs.

The new circuit is based around the
action of a muting circuit which simply
disconnects drive to the loudspeakers for
a few seconds via a heavy-duty relay,
and can be ‘triggered’ by a number of
different events. These events include
power-on, power-off, a DC error, or a
high-frequency (HF) error.

Note that while a power-on event

will trigger the muting action as in
past de-thump circuits, our new
design also responds to a power-off con¬
dition, where the same muting sequence
will occur.

This slightly unusual approach means
that the speakers are immediately dis¬
connected when the power is shut off —
thus preventing any audible clicks and
thumps which can be generated as the
amp’s supply rails begin to fall.

This has the further advantage that if
the power is only momentarily inter¬
rupted, the speakers will be discon¬
nected for a few seconds while the
amplifier’s circuit re-stabilises. When
this situation happens to many
amplifier/de-thump circuit combina¬
tions, the speakers will tend to respond
with a loud thump since the turn-on

muting sequence does not last for its full
period, or may not even occur at all.

By the way, this basic muting cir¬
cuit and its tum-on/tum-off sensing ar¬
rangement is taken almost directly from
the signal muting section of the
Playmaster Pro Series 2 preamp, as pub¬
lished in the October 1990 issue of
Electronics Australia.

This worked well in the Playmaster
preamp, and many readers have ap¬
parently constructed just this part of
the circuit for other signal muting
jobs. Rather than re-inventing a very ef¬
fective wheel, we’ve used it as the basis
of the Protector’s circuit, with a few
minor modifications.

As mentioned above, our circuit is ar¬
ranged so that this muting action is also
triggered by a DC or HF error. These

ELECTRONICS Australia, October 1992

conditions are sensed by additional cir¬
cuits, which monitor signals from both
amplifier channels (the Protector is a
stereo unit) and initiate a muting se¬
quence if the DC or HF level rises
beyond a pre-set point. Note that while a
brief DC or HF error will cause the
speakers to drop out for the muting
period, a sustained fault will cause the
circuit to remain in its muted state until
the problem is cleared.

So if you are using speakers where
the amplifier provides only limited
protection, or none at all, the Protec¬
tor is a very worthwhile investment. It’s
compact, quite inexpensive, and is
suitable for both hifi and PA speakers
driven by amplifiers rated at up to
several hundred watts.

The circuit

Referring to the main schematic
diagram (Fig.l), you can see that the
Protector’s circuit has been arranged in
three main sections. The relay control
and de-thump circuitry is shown at the
top, while the DC and HF detection cir¬
cuits are shown at the centre and bottom
of the diagram, respectively.

As mentioned, the relay control (or
muting) circuit — based around Q1 to
Q6 — is virtually identical to that in the
Pro Series 2 preamplifier, and functions
in the same manner. The heart of the cir¬
cuit is two simple comparators formed
around Q3 and Q4, which sense the
voltage across capacitors Cl and C2,
respectively.

When power is first applied to the
unit. Cl is initially in a discharged state
(ignore Q2 for the moment), holding
the base of Q3 to a low potential. Since
the emitter of Q3 is held at around
5V by ZD1 and its associated resistor
R6, it will be reverse biased (off) until
its base potential rises above about 5.8V
(5.1V + 0.7V).

Therefore, Q3 cannot supply base
current to Q1 via R5 during this initial
period, allowing Q1 to be held in an
off condition by pull-up resistor R4.
The speaker-switching relay RLA is
therefore de-energised, and the speakers
are disconnected. Note that in this
condition, LED1 will be energised via
R1 and the relay coil, indicating a
‘mute’ condition.

After a few seconds have elapsed
however. Cl will have charged to
around 5.8V via R3, causing Q3 to be¬
come forward biased. The increasing
collector current in Q3 will then bias Q1
hard on, energising RLA and connecting
the speakers — LED1 will then extin¬
guish, since Ql’s collector has risen to
around 12 V.

The remaining part of the relay control
circuit is used to re-trigger this muting
sequence in response to a DC or HF
‘eiror’ condition, or if the AC supply has
been interrupted.

The state of the AC supply is detected
via the ‘sense’ line (connected to R12),
which samples the rectified AC input at
the junction of D8 and D9 in the power
supply circuit, as shown in Fig.2.

Fig.2: You have a choice of three power
supply configurations, depending
upon whether the unit is powered from
its own transformer with a single or
centre-tapped secondary winding , or
from the main power transformer of a
‘ host ' amplifier — the PCB
accommodates all three options .

Regardless of which power supply cir¬
cuit is used (supply 1, 2 or 3), the sense
voltage will be a 100Hz waveform
which swings between 0V and a value
representing the peak voltage of the
transformer’s secondary winding — that
is, a rectified AC signal which has not
been filtered.

Returning to the main circuit (Fig.l),

you can see that this signal is applied to
the base of Q6 via R12 and the pull¬
down resistor R13. This in turn means
that while AC is present, Q6 will be
biased on — except for the short dura¬
tions when the sense voltage drops
below about 1.4V, which will occur as
the original AC waveform passes be¬
tween its positive and negative swing.

So while the AC supply is present, Q6
will be turned off for a few milliseconds
at a 100Hz repetition rate — that is, once
every 10ms. The idea here is that during
these brief periods, C2 is allowed to
charge towards the positive rail via Rll,
and is then rapidly discharged as Q6
turns on again. Note that the component
values for C2 and Rll have been chosen
so that C2 will charge to a peak level of
about 2 volts during the few mil¬
liseconds while Q6 is off.

Therefore, the base of Q4 is presented
with a voltage which briefly ramps up to
around 2V at regular intervals. While the
AC signal is present, this waveform will
be ignored by Q4, since it is arranged as
a comparator with a threshold or trigger¬
ing voltage of around 5.8 volts — the
circuit here is identical to that of our first
comparator, based around Q3.

When the AC supply is disconnected
however, Q6 will be off for a longer
period, allowing sufficient time for C2
to charge to the 5.8V triggering level of
Q4. The increasing current in Q4 will
then bias Q5 hard on, which in turn
drives Q2 into saturation.

Since Q2 is connected directly across
the main turn-on delay timing capacitor
Cl, this is immediately discharged. So
Q3 turns off, and the relay drops out as
detailed above. Thus the muting relay
will disconnect the speakers just a few
milliseconds after the AC supply is dis¬
connected. Note that as the Protector’s
DC supply falls, the circuit will not have
enough power to re-energise the relay, or
complete the power-up timing cycle.

On the other hand, if the AC supply is
only interrupted rather than discon¬
nected for an extended period, the circuit
will complete the turn-on timing cycle
as if the unit had been just switched on.
This is because Cl is immediately dis¬
charged once the circuit has detected a
lack of AC supply, and will then slowly
charge towards the 5.8V triggering level
if power has been is re-applied.

In practice, this means that if you (say)
inadvertently turn the amplifier’s mains
switch off then rapidly on again, the
Protector will mute your speakers for the
full de-thump timing period — no
chance of nasty thumps and bangs
through the speakers as the amp
recovers from the drop-out.

ELECTRONICS Australia, October 1992

Flexible loudspeaker protection circuit

Since the AC-off detector (based
around Q4) simply pulls the base of Q5
low to initiate the Protector’s muting se¬
quence, this is a convenient point to con¬
nect the output of the DC and HF error
sensing circuits, based on ICla/b and
IClc/d respectively.

The LM339 comparators have open-
collector outputs (that is, an NPN output
transistor with its emitter connected to
ground), enabling all four comparators
to drive the same ‘trigger’ line which
connects to the collector of Q4 via R9
and isolating diode D3. We therefore
have a simple OR scheme, where if the
output of any of the comparators — or
Q4 — goes low, Q5 will be biased on
and the muting sequence activated.

Note that LED3 (‘fault’) and its as¬
sociated limiting resistor R20 is con¬
nected to the output of the four
comparators, so that an extended DC
or HF error will be indicated as a
fault condition — in other words, it
shows that if you had bypassed the
Protector at this time, your speakers
would probably fry...

By the way, D3 has been included to
prevent Q4 from activating LED3
when the AC supply is interrupted, as
this could hardly be considered as a
fault condition.

It is definitely a cause for concern
however, if a significant DC level ap¬
pears at the loudspeaker terminals. This
condition is sensed by a circuit formed
around ICla for the right channel, and
an identical arrangement for the left
channel based on IClb. The following
description concerns the right channel.

The amplifier output, at the contacts
of RLA, is connected to both Q7 and Q9
via the current limiting resistor R15 —
which also forms a low-pass filter in
conjunction with C5. Whenever the out¬
put of the amplifier is driven to more
than +0.6V by a DC or low-frequency
AC signal, then Q7 is biased on, thereby
shorting current through R16 away from
the base of Q10, turning it off.

In a similar fashion, if the input
swings less than -0.6V, then Q9 is biased
on and supplies base current for Q8,
which in turn again removes the drive
from Q10, turning it off. As in the
case of the AC sensing circuit, a
timing capacitor is then allowed to
charge towards a comparator’s trigger¬
ing voltage.

In our DC sensing circuit, timing
capacitor C6 will charge via R17 to
comparator ICla’s triggering point of
6V, as set at its positive input (pin 7) by

the voltage divider formed by R18 and
R19. If the capacitor’s voltage does
reach 6V, ICla will drive its output to a
low level (since we are using the invert¬
ing input at pin 6), thereby supplying
base current to Q5 via D3, R9 and R8.
As previously discussed, this will cause
the muting relay to activate.

The time constant associated with R17
and C6 means that if Q10 is off for more
than about 100ms, then the voltage
across C6 (the comparator input) will
reach the 6V trigger level, and a ‘fault’
condition will occur. Since Q10 is
turned off by either Q7 or Q8/Q9 in
response to a positive or negative input
level, respectively, then an input transi¬
tion (+ve to -ve) must occur within
this period in order to avoid a fault
condition. The transition will cause both

Input Voltage Range R30, R31

71 - 80V

330 ohms

61 - 70V

270 ohms

51 -60V

180 ohms

41 -50V

120 ohms

31 - 40V

82 ohms

15-30V

link (omit ZD2
and ZD3)

Fig.3: Use this table as a guide to the
value of the 5W dropping resistors
(R30 and R31) in Power Supply 3, as
shown in Fig.2. A 200W (into eight
ohms) amplifier might have a positive
supply rail of say 68V, meaning that
270 ohm resistors should be used.

Q7 and Q8 to be off as the input
passes through 0V, allowing Q10 to dis¬
charge C6.

In practical terms, this means that for
input signals which have a frequency
greater than about 5Hz, the signal volt¬
age will pass through 0V within the re¬
quired time period, and the comparator
will not be triggered. For signal fre¬
quencies less than about 5Hz however,
which of course includes DC, the cir¬
cuit will quickly trip into its fault con¬
dition and remain in that state until the
problem is cleared.

The HF detecting circuit shown at the
bottom of the schematic uses a much
simpler approach in sensing an error
condition. Here, the signal from the
amplifier first passes through a second-
order high-pass filter composed of C9,
R24, CIO and R25 (referring to the
right channel circuit), which is set to
around 40kHz.

The resulting high-frequency energy

(if present) is then passed to a simple
half-wave rectifier formed by D4 and
R26, and the consequent DC signal
smoothed by Cll and passed to the com¬
parator input at pin 4 (IClc).

As you would expect then, if the
amplifier is generating enough HF ener¬
gy to produce a DC level at pin 4 which
is greater than the reference voltage at
pin 5, the comparator will drive its out¬
put to a low level and trip the muting
circuit. Note that in this circuit, the ref¬
erence or trigger level is set by trimpot
RV1 rather than a fixed voltage divider,
as in the DC sensing circuit. This allows
the user to adjust the Protector’s sen¬
sitivity to unwanted supersonic signals
(more of this later).

By the way, D5 has been included to
prevent damage to the comparator’s in¬
verting input in the event of an extreme¬
ly large high-frequency signal appearing
at the amplifier’s terminals. In this situa¬
tion, D5 will become forward biased,
preventing the rectified signal from ex¬
ceeding a level of about 12.6V.

That’s about it for the main circuit.
The remaining components involve the
power supply, and the various power
transformer options as shown in Fig.2.

Power supply 1 will most likely be
used if you have elected to run the
Protector from its own small trans¬
former. A single secondary winding is
used here to drive a full-wave rectifier
formed by diodes D8 to Dll, with the
resulting rectified AC connected to the
‘sense’ line, and to point X via Link 3.

Note that in all of the power supply
configurations (1, 2, and 3) the
Protector’s 12V supply is ultimately
derived from point X. Considering
power supply 1 for the moment, the un¬
filtered DC is passed to isolating diode
D2 (in Fig.l), which in turn feeds
smoothing capacitor C4.

The resulting DC level supplies the
7812 regulator IC2, which produces the
circuit’s stabilised +12V supply rail.
Further smoothing is provided by C3,
while LED2 and its limiting resistor R14
provide a ‘power on’ indication.

Power supply 2 is intended for use
with a separate transformer which has a
centre-tapped secondary, rather than a
single winding as used with supply 1, or
where you intend to power the Protector
from a low-voltage winding on the
amplifier’s own transformer — such as
its pre-amp power supply winding.
Thanks to the centre-tap, only two
diodes (D8 and D8) are needed for a full
wave rectifier in this case. The sense line

ELECTRONICS Australia, October 1992

and unfiltered DC (point X) connections
are the same as in power supply 1.

The final power supply configuration
(supply 3) has been included for situa¬
tions where the Protector is to be
powered directly from an amplifier’s
transformer, but a separate low-voltage
winding is not available — such as in
slave or PA amplifiers based on power
amp modules. Here the sense line is con¬
nected to its own full-wave rectifier
based on D8 and D9, while point X is
supplied by a simple voltage drop-
ping/pre-regulator scheme driven from
the amp’s DC supply rail.

If the amplifier has a DC supply rail of
say 70V (a typical figure for a common
300W amp module) and both R30 and
R31 have a value of 270 ohms, then
about 96mA will flow through ZD2 and
ZD3 if there is no load at point X: I=(70-
18)/(270+270). However, the load at
point X — the Protector’s main circuit
— draws around 90mA when the relay is
energised, leaving 6mA flowing through
ZD2 and ZD3.

As you would expect from this type of
voltage stabilisation circuit, the zener
current will increase as the load current
drops (say, when the relay is de-ener¬
gised), and the voltage at point X is
maintained at 18V. While the above ex¬
ample can be used to calculate the ap¬
propriate resistors for other amplifier
supply rails, we’ve included a table
(Fig.3) showing suggested component
values for a wide range of DC input vol¬
tages, to make things a little easier.

So whether you use power supply 1, 2
or 3 will depend upon how you plan to
install the Protector. If you want a stand¬
alone unit that can be used with any
amplifier, it will need its own trans¬
former which should be wired as shown
in power supply 1 for a single secondary
winding (12V to 20V AC), or supply 2
for a centre-tapped secondary (12-0-12V
to 20-0-20V AC).

On the other hand, if you intend to in¬
stall the Protector inside an existing
amplifier, you’ll need to use the power
supply 2 arrangement where a low-volt-
age centre-tapped secondary winding is
available, or power supply 3 where only
the main (higher-voltage) winding is ac¬
cessible.

Of course if there is sufficient space
inside the amp’s case, you could install
a small transformer to run the Protec¬
tor, and connect its primary winding to
the output side of the amp’s main
power switch.

Construction, options

All of the Protector’s components (ex¬
cept the power transformer, if used) fit

onto one small printed circuit board
(PCB) which measures 115mm x 64mm,
and is coded 921p8. The components are
quite tightly spaced on the board in
order to keep its overall dimensions to
a minimum, so the smaller parts (resis¬
tors, diodes, etc) will need to be in¬
stalled first.

You will need to decide which of the
power supply configurations suits your
requirements, and fit the components as
shown in the component overlay
diagram, while referring to the
schematics shown in both Fig.l and
Fig.2. As usual, take particular care with
the orientation of any polarised com¬
ponents, such as the electrolytic

PARTS LIST

1 PCB 64mm x 115mm, coded 92lp8
1 PDT heavy-duty relay, 150 to 200 ohm
coil resistance
1 Small TO-220 heatsink

Resistors

All 0.25W 5%: 8 x 470k, 1 x 220k,

4 x 100k, 4 x 82k, 3 x 33k, 1 x 18k,

3x 12k, 2x 10k, 3 x 1.8k
1 200k horizontal-mounting trimpot

Capacitors

1 470uF 25V PC-mount electrolytic

2 22uF 16V PC-mount electrolytic
4 0.22uF metallised polyester

1 O.luF metallised polyester

2 220pF ceramic
4 lOOpF ceramic

Semiconductors

1 LM339 quad comparator
1 7812 three-terminal regulator
10 BC547 NPN transistor

3 BC557PNP transistor
1 BC328 PNP transistor

4 1N4002 power diode

5 1N914 signal diodes

1 5.1V 1W zener diode

3 5mm LEDs: red, yellow, green

Extra parts for power supply 1

2 1N4002 power diode

Extra parts for power supply 3

2 9.1V 1W zener diode
2 5W resistors; see table (Fig.3)

capacitors and all of the semiconductors
— note that there are both NPN
(BC547) and PNP (BC557) transistors,
and the relay-driving transistor Q1 is a
more robust BC328.

If you have elected to use power supp¬
ly 3, measure the amplifier’s positive
supply rail, and select the appropriate
5W resistor combination from the table
in Fig.3. Of course you can work out the
values yourself if you prefer. Note that
these resistors will dissipate around 2.5
watts each and will get reasonably hot
while the Protector is operating, so they
should be fitted at least couple of mil¬
limetres proud of the PCB, so as to

promote cooling. The zener diodes on
the other hand, will only be handling
less than lOOmW each and should
remain quite cool.

Note also that there are three links on
the PCB. Link 3 is used to configure the
power supply, and is not fitted in the
power supply 3 arrangement. Converse¬
ly, links 1 and 2 are always included,
and are used to cater for the variation in
contact-to-pin wiring of the commonly
available relays.

To set the position of links 1 and 2,
you will need to identify which pins cor¬
respond to the normally-open contacts
on the relay that you intend to use —
quite a simple job with a multimeter.
While looking at each set of contacts,
establish which pin connects to the nor-
mally-open contact itself (rather than the
moving-arm contact), and install the link
in this position.

As shown in the circuit diagram
(Fig.l), this means that the Protector will
sense the incoming signal from the
amplifier so that in the case of an ex¬
tended HF or DC fault, the circuit will
remain triggered for the duration.

Wiring the contacts in this fashion also
means that you have the option of con¬
necting the relay’s spare contacts (nor¬
mally closed) to the amp’s negative or
common line, for extra safety where a
high-powered amp is used.

The theory here is that if a large DC
fault occurs in the amplifier, an arc
will probably occur as the moving con¬
tact opens the circuit to the speaker. In
a high-powered amp in particular,
where the supply rails may be 70V or
more, the arc is likely to be maintained
even when the contacts are fully open
and the speaker would still be effectively
connected to the faulty amp — not a
happy scenario...

With the closing contacts connected to
the common line (the amp’s negative
terminals) however, a short is applied
across the speakers when the relay is de¬
energised, shunting the arc back to the
amp. If the arc is still maintained, the
amplifier will blow its protective fuses
— thereby saving your speakers.

While this ‘crowbar’ approach might
sound rather destructive, remember that
your speakers will invariably be more
expensive to repair than your amp —
and besides, it’s probably in deep trouble
anyway, due to the DC fault which
started events in the first place.

The relay itself must have contacts of
a suitable rating for the amplifier in
question, so take note of these specifica¬
tions when making your choice. In this
respect, we have arranged the PCB
layout to suit two of the more common

ELECTRONICS Australia, October 1992

Flexible loudspeaker protection circuit

relays available from component sup¬
pliers: the large ‘heavy duty’ DPDT
relay featuring 10A contacts, and the
smaller ‘high power’ relay which offers
contacts rated at 5A. These will suit
high-and medium-power amplifiers,
respectively.

Alternatively, you may have a suitably
rated relay in your junk box which
doesn’t match the PCB layout. In this
case the relay could be mounted off the
board, and short lengths of heavy duty
cable run from the PCB pads to the relay
pins. Of course the relay coil must have
a 12V rating, and if its resistance is not
in the range of about 150 to 200 ohms,
you will have to measure the current
drawn by the Protector’s circuit and re¬
calculate the values for R30 and R31 (if
you are using power supply 3).

Note that both the current drawn by
the Protector, and its DC input voltage
will determine the dissipation in the 12V
regulator (IC2), which should normally
fitted with a small heatsink. If the input
voltage is about 18V, such as in power
supply 3, and the relay coil’s resistance
is in the range mentioned above, then the
IC will be handling less than 1W.

On the other hand, you may have
elected to use a dedicated transformer
(supply 1 or 2) with a secondary rating

of 20V AC, which leads to a DC input
voltage of around 28V and a higher dis¬
sipation in the regulator chip. While this
is still only about 1.5W with the
specified relay, remember that a lower
coil resistance will increase the figure
and a larger heatsink may be needed —
particularly if you plan to install the unit
in a case which offers little in the way of
ventilation slots.

If you have in fact elected to fit the
Protector and its matching transformer
in a box, the 240V mains wiring must be
connected in a safe manner. The mains
cable should pass through the box wall
via a suitable grommet, then be solidly
anchored inside using a ‘P-clamp’ or
similar mounting hardware. The active
and neutral leads can be terminated to
the transformer’s primary winding, and
any exposed connections covered with
some form of insulation.

The mains earth lead (green/yellow)
should then be reliably connected to
the power transformer’s body via a
solder lug, which should be attached to
the transformer frame via a nut, bolt
and locking (‘star’) washer. If you are
using a plastic rather than metal box
however, both the transformer and the
earth lug should be solidly bolted or
screwed (with lockwashers) to a small

section of aluminium plate, which in
turn is mounted into to the case via
separate bolts or screws. In this way,
the electrical connection between the
mains earth and the transformer is
maintained, regardless of the condition
of the case material.

Note that we have elected to leave the
Protector’s common line (0V) ‘floating’,
rather than connecting it directly to the
mains earth at the transformer frame.
This is because when the unit is con¬
nected to an amplifier (that is, once it’s
installed), this line will return to the
mains earth via the amp’s 0V line.

Alternatively, if you have one of those
‘double-insulated’ amps with a two-core
mains lead, then the Protector’s circuit is
happy to electrically ‘float’ with the
amp’s internal circuitry — a typical off-
the-shelf transformer to suit the Protec¬
tor will have an insulation rating of least
3.5kV, by the way.

To finish installing the Protector into a
box, securely mount the PCB inside, fit
the three LEDs to the front or top panel,
then complete the remaining wiring as
shown in the component overlay
diagram and Fig.2 (for the power supp¬
ly). Of course, you will need to fit a
series of speaker wire connectors to the
box, which should be wired to the PCB
as shown. The actual connectors could
be made up from a strip of insulated
tagstrip, a number of banana sock-
ets/posts, or a four-way moulded
speaker terminal (the type with spring-
loaded crimp connectors).

If you have decided to install the
Protector inside an amplifier, you should
find the job to be quite straightforward.
In this case, the PCB should be mounted
in close proximity to the speaker outlet
terminals, and the existing wiring
modified so that the Protector’s relay
contacts will mute (disconnect) the out¬
put to the speakers as required. The
status LEDs can be installed in some
visible position, or simply left out of the
circuit since they play no directly active
part — the Protector will draw a little
less current, however.

Then connect the unit’s ‘AC’ inputs to
the secondary winding of the amp’s
power transformer, and the ‘CT’ connec¬
tion to the amp’s 0V line, which ul¬
timately connects to the secondary’s
centre-tap.

Note that power supply 2 in Fig.2
should be used to power the Protector
from an amp’s low-voltage secondary
winding (say, its preamp supply), while
the circuit shown as power supply 3 is

Follow this component overlay diagram during construction . Note that all of the
optional components are shown installed ' so you will need to decide which
configuration suits your needs, and fit only those parts — for example, link 3’ is
not used at the same time as R31.

ELECTRONICS Australia, October 1992

A full-sized reproduction of the Protector’s PCB pattern , for those intrepid
constructors who make their own boards.

designed to suit an amplifier’s higher-
voltage secondary winding (which sup¬
plies the power amp stage).

By the way, the ‘common’ connection
shown on the PCB overlay does not
need to be connected when the Protector
is installed inside an existing amplifier,
since the centre-tap connection (CT)
links the OV lines between the two cir¬
cuits as required.

When the unit is powered from a
separate transformer however, the
‘common’ connection on the PCB
should be wired to the left or right nega¬
tive speaker connections, so as to con¬
nect the OV lines together.

Also, if the amplifier in question is of
a valve design, you will need to re-wire
the relay connections so that a resistive
load is switched in place of the speakers
when muting occurs. This is because
valve amps can suffer internal damage
(through arcing) when the output load is
disconnected.

Note that while the Protector’s HF
sensing is useful for a valve amp, its
other features are of little benefit —
these amps generally cannot deliver a
DC level to the speakers, and don’t tend
to produce tum-on/off thumps.

Commissioning

Once the Protector’s circuit is com¬
plete and the PCB hard-wired to its ex¬
ternal connections, it may be worthwhile
to double check the relay contact wiring
in particular. If this is correct, the relay’s
moving arm contacts will ultimately
connect to the speakers, while the nor-
mally-open contacts should connect to
the amplifier outputs.

Note that links 1 and 2 must also be
connected to the normally-open con¬
tacts, so that the Protector will be sens¬
ing signals at the amplifier outputs,
rather than at the speaker connections.

These checks are rather important,
since a mistake in the wiring could ac¬
tually short the amp’s output, thereby
blowing the protective fuses, or even
causing the destruction of its output
transistors. By the way, if you have
wired the normally-closed contacts to
the common (negative) line for arc-sup¬
pression purposes, then these connection
should also be checked.

Once you are satisfied with your
wiring, turn RV1 to its mid position and
apply power to the Protector — that is,
turn on the associated amplifier. At this
stage, both the green (power) and the
yellow (mute) LEDs should immedi¬
ately illuminate, indicating that the 12V
rail is present and the relay has not yet
engaged, respectively.

Then after a few seconds, the mute
LED should go out and the relay will
pull-in with a quite audible ‘click’. Note
that the red (fault) LED should not il¬
luminate, except for perhaps a brief flash
when power is first applied — unless of
course, the amplifier already has a HF or
DC fault!

If you wish to check the action of the
DC sensing circuit, you’ll need to tem¬
porarily disconnect links 1 and 2, then
connect a battery or other DC source
to the Protector’s error sensing inputs
(the junction of R15 and C9 for the right
input).

The relay should almost immediately
drop out and the ‘fault’ LED should il¬

luminate; this condition should remain
as long as the DC source is connected.
If the DC level is only briefly applied,
the relay should drop out for a few
seconds as the Protector goes through
its muting cycle.

The HF sensing circuit is a little more
difficult to check, unless you have an os¬
cillator which can deliver a couple of
volts at frequencies above the audio
band. If such an instrument is at hand,
connect the signal to the Protector’s
input as detailed above and check that
the circuit behaves in the same manner.
Note however that you may need to in¬
crease the circuit’s HF sensitivity by ad¬
justing trimpot RV1.

How RV1 is finally set for normal
operation will need to be determined by
experimentation, since the circuit tends
to respond to large transient signals as
well as a continuous burst of high-fre¬
quency energy. Try playing a high-
quality source (say, a CD player) at your
typical listening level, and increasing the
protectors HF sensitivity (with RV1)
until the circuit begins to occasionally
mute. Then back-off the adjustment a lit¬
tle, so that it will not trip under normal
circumstances.

Alternatively, you might like to con¬
centrate on the Protector’s ability to
detect the HF energy produced by exces¬
sive clipping. In this case, connect your
amplifier to a dummy load, increase the
drive level until hard clipping occurs,
then adjust RV1 until the circuit trips
into muting. You should then check that
the Protector will not also trip under nor¬
mal listening conditions.

If the above methods are not satisfac¬
tory, or you can’t be bothered with such
fine-tuning, simply leave RV1 at its mid¬
position. If the circuit is working cor¬
rectly, you can be sure that a substantial
(that is, tweeter damaging) level of HF
energy will be detected as an error, and
the speakers disconnected.

Since this setting of RV1 corresponds
to a peak signal of 6V, then a HF input
level greater than 4VRMS will trip the
circuit — this represents a theoretical
power level of only 2 watts into an 8
ohm tweeter. The HF circuit will also
trigger at frequencies below 40kHz, but
with a reduced sensitivity since the filter
rolls off at around 12dB per octave.

Once you are satisfied that the Protec¬
tor is working correctly, and your instal¬
lation job is complete, you can move on
to the more important business of listen¬
ing to music.

Since your new Protector circuit is
watching over those expensive loud¬
speakers, you can sit back and enjoy the
experience of worry-free listening. ❖

ELECTRONICS Australia, October 1992

Circuit & Design Ideas

Interesting circuit ideas from readers and technical literature. While this material has been checked as far as possible for feasibility, the circuits
have not been built and tested by us. We therefore cannot accept responsibility, enter into correspondence or provide further information.

TV headphones amp

My friend has a hearing problem, which
presented no problem with his original
TV which came equipped with a head¬
phone jack. But when this set played up
and was replaced, the new model had no
such provision.

His new set was of the now-common
live chassis type, necessitating an isolation
device if lapping across the loudspeaker.

This would have been no problem, ex¬
cept that tampering internally with the set
would certainly have made void his war¬
ranty. Instead, I built the circuit shown.

An electrct microphone was used to
pick up the sound signal. This type of mic
was used because of its low cost and
resilience to magnetic and electric fields
(e.g., frame buzz and 50Hz hum). It is
mounted as close to the front of the
speaker as practical, and wired back to the
amp via screened cable.

The amplifier is built around the LM386
chip, which needs only a few components
for smoothing, power supply and audio
shaping.

The 33k/22nF combination provides
negative feedback for high frequency,
such as horizontal pickup and annoying

Telemetry converter

This circuit was designed to convert the BCD output of a ther¬
mocouple thermometer to serial data for logging by a PC. It uses
an AY-3-1015 UART and a few supporting chips to relay the
logic state of eight points through the serial line to the computer.

The UART acts as a parallel to serial converter. Conversion is
triggered by sending two control bytes from the computer. The
falling edge of the first byte arrives at SI and RDAV-bar, forcing
DAV low. This strobes eight bits on Din (10-17) into the shift
register and serialises them to SO. The conversion returns two
bytes but the first byte should be discarded and the second byte
used. The input levels should be TTL.

Data rates ranging from 19,200 to 300bps can be selected by
jumpering the appropriate output of the frequency divider to the
UART clock pins. The computer port should be set for eight bits
(NB1 and NB2 at logic ‘ T), no parity (NP logic 4 1 ’) and one stop
bit(TSB logic ‘0’).

More than eight points can be monitored by using the Dour out¬
puts (00-07) to control input multiplexers. For example, using
one bit to control each multiplexer allows 64 points to be
monitored. In this case, each control byte should have only one
bit on. The Dour outputs can also be assigned for device control.
A MAX-232 can be substituted for the 1488/1489 chips, in which
case only a 5V supply is required.

Ken Yap,

Lane Cove, NSW $40

DSE 2851 1N4004

R1
470

sets the amplifier gain to give sufficient
signal at the headphones — with volume
to spare.

Hum pickup is minimised by careful

transformer frame and to the body of the
on/off switch, for safety.

Warwick Talbot,

Toowoomba, Qld $40

ELECTRONICS Australia, October 1992

Heightened stereo effect

To emphasise the stereo effect of an
amplifier, an extra set of imaging speakers
are often used, driven out of phase, and set
up to produce destructive interference of
the left channel at the right ear, and
vice versa.

This circuit achieves the same effect, but
removes the need for the second set of
speakers. It does this by adding smaller,
delayed versions of the left and right
signals to the right and left outputs.

Improved adjustable
3-pin regulator

The traditional method of increasing the
output voltage of a three-terminal
regulator is to connect the ‘GND’ pin to
the junction of two suitably-chosen resis¬
tors in series across the output
Unfortunately, the quiescent current of
the regulator makes it necessary for these
resistors to be of quite low value in order
to ‘swamp’ this current
This results in excess current consump-

When the delay is properly set to account
for the path length difference of the
speakers to each ear, the stereo effect is
heightened greatly.

The input signal is first buffered by IC1,
then passed to IC2, an MN3001 Bucket
Brigade Device (BBD). The input level
and biasing are set by the 10k pots for each
channel (input pins 3 and 5), and are ad¬
justed for the lowest distortion and best
signal-to- noise ratio.

The clock signal for IC2 is produced by
a 74C14 hex Schmitt trigger, with the

tion and the need to ‘fine tune’ the resistor
values for the quiescent current of the in¬
dividual regulator. And in some variable
circuits, it can be hard to find pots with ap¬
propriately low resistances.

By the simple addition of a BC559
transistor as shown, about 99.5% of the
quiescent current can be diverted away
from the voltage divider, eliminating
these problems.

By assuming that both Iri and Ir2 are ap¬
proximately 1mA, we can find suitable
values for R1 and R2.

R1=Vri/1itiA
=(VRi)k ohms

R2=(VouT-VRi)k ohms
where Vri=Vreg+0.65, and Vreg is the
regulator’s nominal voltage.

This circuit has the same line and load
regulation and stability as the traditional
one, and the only disadvantage is that the
regulator dropout voltage is increased to
about 3 V.

Bob Parker,

Carlton, NSW $40

period set by the 200 ohm resistor and the
lk pot This produces a delay of ap¬
proximately 0.1-0.8ms.

The output from IC2 is amplified by
8.5dB by IC4 to account for losses in the
BBD. It is also inverted and filtered above
20kHz to remove any clock noise from the
signal. Each channel is then mixed, via
IC5, with the delayed version from the
other channel. The imaging volume is set
by the 50k dual-ganged pot.

The appropriate delay can be easily
worked out by simple maths. Find the
path difference between each speaker to
one ear and divide it by the speed of
sound, 330ms 1 .

More simply, drive one channel with a
tone, and the correct settings will be ob¬
vious when the other ear is blocked —
there will be a noticeable volume drop.
Note, of course, that the listener must be in
line with the middle of the two speakers.

Mark Kelly,

Camberwell, Vic $45

Computer programs capable of
simulating the performance of complex
analog circuits can now be run on many
personal computers, heralding a new era
in the design of electronic equipment.

Find out more about this rapidly grow¬
ing technology, with our new publication -

PC-Based Circuit Simulators

Available from your newsagent or by
mail order. Price in Australia $2.95, plus
$2 when ordered by mail, from -

The Book Shop,

Federal Publishing Company,
PO Box 199,
Alexandria, NSW 2015

ELECTRONICS Australia, October 1992

MITH

ELECTRONICS

SENSAffdNAL

ne w kits

UNIVERSAL MOTOR SPEED 9 B
CONTROLLER

This easy to build kit is designed for regulating the speed on
heavy-duty power tools. It’s ideal for circular saws, electric
drills, lawn edgers, jig-saws, grinders and other appliances
which are rated at 5 amps and have a ‘brush type' motor. This
new improved design has a higher current rating and uses a
Triac rectifier instead of a SCR. As well, it monitors the ‘back-
EMF' voltage from the motor, so though the drill speed is
controlled, it won’t bog down when the going gets tough.
Complete with deluxe pre-punched screened front panel,
components, PCB and flush mounted mains socket.

* *

FOR BRUSH
MOTORS UP
* TO 5 AMPS

K-3085 £

•

£ ;

H •

* ♦ %

MIN MAX

-&-SPEED CONTROLLER—

D*CK SMfTM ~_

“•pr-iiLfic raomcs-O—

Also Available Individually

Insulated Triac (BTA 10-600B)

As used in K-3085 $C95

Cat Z-4515 W

3V 2 DIGIT 9
PANEL METER H™

An easy to build kit which is perfect for
monitoring voltages, including
anything from power supplies to car
batteries. This general purpose panel
can be built to read voltage up to +/-
200V DC or current up to 2A (or both
with suitable switching). It’s ideal for
the hobbyist, student and any
application where you need to monitor
voltage or current accurately and
precisely. Complete with LCD screen,
all components, PCB and a 9V battery
snap. (Requires 9V battery)

*VrtY»V*V*V-■?

Also Available Individually

Liquid Crystal Display with data sheet.
As used in K-7502

Cat Z-4175

$ 14 95

MINI 1.5VTOW 9
DC CONVERTER

Here's an easy way to replace those expensive
9 volt batteries with cost-efficient 1.5 volt cells.

This easy to build kit uses just 3 components
and allows any type of 1.5V cell (AA.C.D.N or
AAA) to replace a more expensive 9V battery.

What’s more, the PCB measures just
17 x 43mm and fits easily inside a 9V
battery compartment. Cat K _ 3231

$095

AUDIO SWEEPER 990

A buget-priced kit for audiophiles, sound experts, enthusiasts...
in fact anyone involved or interested in sound. This affordable
audio test system analyses the performance (mid, treble &
bass) of speakers, speaker enclosures, filter circuits and room
acoustics. It consists of a sweeping audio test signal generator
and a metering amplifier which measures the results. The kit
comes complete with a deluxe pre-punched front panel, plastic
instrument case, PCB, hardware (including dB meter) and all
components.

Hf*

$ 109

Cat K-7352

Semiconductor Of The Month!

TDA 1514A 50 WATT/RMS HIGH
POWER AMP As used in K-5600

This new hybrid module semiconductor has an inbuilt
SOAR (safe operating area) protection and
extremely quiet operation. Data sheets available In
all stores.

$4095

Cat Z-6117 |

iStSURm SZM

Please contact your nearest store
for availability

—

SCANNER BOOKS

Register of Government Radio Frequencies NSW & ACT
Scanner Fanatics Frequency Register ot NSW
Scanner Fanatic Frequency Register ot Vic
Australian Radio Frequency Handbook

DATA & REFERENCE BOOKS
Towers International Transistor Selector
Resistor Colour Code Chart
Philips Linear Databook
Philips 1C & Semiconductor Reterence Guide
SGS-Thompson CMOS 4000 Databook
SGS-Thompson SCR & TRIACS Databook
SGS-Thompson DIODES Databook
SGS-Thompson Small Signal Transistor Databook
Motorola RF Devices Databook
Motorola RAMs & EEPROMS Databook
Motorola Thyristors Databook

ELECTRONICS & HOBBY BOOKS

Electronics Tips & Techniques

Mastering 1C Electronics

Home Remote Control Projects

Basic Electronics Theory

101 Opto Electronics Projects

Encyclopedia ot Electronic Circuits Vol.3

Introductory Electronics

Aviation & Space Science Projects

Electronics tor Model Railways

14 FM Bugs to Build

Data Sheet on PCB Making

Guide to NiCad Batteries

Wire & Cable tor Electronics

RF Interference Handbook

SHORTWAVE RADIO BOOKS
Shortwave Listening Guidebook
Passport to World Band Radio
World Radio & TV Handbook
Radio In Australia

AMATEUR BOOKS
Yaesu Amateur Radio Log Book
Yaesu Ham Operators World Map
ARRL YAGI Antenna Design
ARRL Antenna Handbook 16th Ed.

ARRL Radio Handbook, 1992 Ed.

Secrets ot RF Circuit Design

Your Gateway to Packet Radio

AX-25 Packet Radio Protocol

W.I.A. Into Electronics

W.l A Novice Electronics

W.IA 1000 Questions tor Novice Candidates

W.I.A 500 Questions for AOCP Candidates.

SATELLITE TV BOOKS
Satellite TV - Pacific Region
ARRL Satellite Antology

CB RADIO BOOKS
The Screwdriver Experts Guide
CB International PLL Data Book
Understanding CB Radio
CB EPROM Data Book

LEARN ELECTRONICS THE FUNWAY
Funway Into Electronics Vol.l
Funway Into Electronics Vol.2
Funway Into Electronics Vol.3

B-4100

$29.95

B-4102

$24.95

B-4104

$24.95

B-9601

$14.95

B-4600

$49.95

B-1000

$ 5.95

B-5553

$49.95

B-5552

$18.95

B-5560

$24.95

B-5564

$24.95

B-5566

$29.95

B-5568

$19.95

B-5400

$29.95

B-5402

$19.95

B-5404

$19.95

B-1600

$29.95

B-1612

$39.95

B-1614

$29.95

B-1615

$39.95

B-1617

$29.95

B-1760

$54.95

B-3635

$18.95

B-6702

$16.95

B-3642

$ 2.95

B-3650

$ 3.50

B-6005

$ 1.25

B-6040

.95c

B-1618

$49.95

B-2401

$19.95

B-2040

$29.95

B-2050

$34.95

B-2092

$35.95

B-2300

$ 4.90

B-2029

$ 9.95

B-2030

$ 6.95

B-2105

$29.95

B-2209

$39.95

B-2225

$49.95

B-2311

$39.95

B-2402

$24.95

B-2403

$14.95

B-2313

$ 9.95

B-2317

$ 9.95

B-2316

$ 9.95

B-2318

$ 9.95

B-2321

$29.95

B-2400

$15.95

B-2324

$19.95

B-2326

$19.95

B-2327

$36.95

B-2329

$14.95

B-2600

$ 4.95

B-2605

$ 6.95

B-2610

$ 6.95

THE COMPLETE
MEMORY MANAGER

MfATICfc HU I AtSTKU

~WUKJ

BOOKS

BOOKS
BOOKS “nmm

OOKSBOOKS

OOKSBOOKS
OOKSBOOKS

onmooKs

BOOKS
BOOKS

Frequencies

t lUW-ACT

BOOKS BOOK
BOOKS BOOK
BOOKS BOOK

COMPUTER BOOKS

The Complete PC Memory Manager
RS232 Made Easy. 2nd Ed.

PC Architecture & Assembly Language

GW BASIC Primer Plus

DOS 5.0 User's Guide

IBM PC Configuration Handbook

The 486 Book

Quickstart Works For Windows
Quickstart Windows 3.1
Quickstart WordPerfect for Windows
WordPerfect tor Windows By Example
WordPerfect 5.1 Quick Reterence
Microsoft Word 5 Quick Reference
MS.DOS 5 Quick Reterence
Norton Ultilities 6.0 Quick Reference
Lotus 1-2-3 Release 3.1 Quick Reference
Hard Disk with DOS 5.0 Quick Reterence
PC Tool 7.0 Quick Reterence
Guide To XTREE Quick Reference
Windows 3.1 Quick Reference
QUATTRO PRO 4 Quick Reference
The Complete DOS 5 with Batch File Disk
Atari Portfolio Guidebook
A Kid's Guide to Computers

GAMES BOOKS

Leisure Suit Larry Bedside Companion
Beyond the Nintendo Masters
Mastering Nintendo Video Games
Tricks ot the Nintendo Masters
The Complete Nintendo Video Games Guide
Winner's Guide to GAME BOY
Winner's Guide to SEGA

B-6097

$39.95

B-6098

$49.95

B-6099

$28.95

B-6100

$59.95

B-6101

$39.95

B-6203

$59.95

B-6205

$69.95

B-6385

$24.95

B-6391

$24.95

B-6397

$29.95

B-6398

$59.95

B-6400

$19.95

B-6402

$19.95

B-6404

$19.95

B-6407

$19.95

B-6408

$19.95

B-6413

$19.95

B-6415

$19.95

B-6416

$19.95

B-6417

$19.95

B-6418

$19.95

B-6500

$69.95

B-8700

$39.95

B-6700

$19.95

B-6900

$22.95

B-9800

$19.95

B-9802

$18.95

B-9804

$19.95

B-9806

$19.95

B-9808

$18.95

B-9810

$18.95

B1374

MULTIMETERS

Regarded by industry professionals as the most forgiving multimeters ever made!”

Fluke 12 Multimeter Fluke 10 Multimeter

With a 3 % digit (4000 count) display
and a V-check which automatically changes
modes What's more, it has continuity
capture which records intermittent opens and
shorts as brief as 250mS. In addition, the
min/max record and time stamp lets you
capture precisely what occurred and when
Hook it up, walk away, then come back and
find out what happened it's that easy!

Cat Q 1612

159

2 YEAR WARRANTY!

Specifications

DCV: 4000mV, 4V, 40V, 400V, 600V
Accuracy: (0 9% +2 tor4000mV& 4V
range) (0.9% + 1 for 40V, 400V & 600V
ranges)

ACV: 4000mV, 4V, 40V, 400V, 600V
Resistance: 400 Ohm, 4K Ohm, 40K Ohm
400K Ohm, 4M Ohm, 40M Ohm
Capacitance: luf, lOuf, lOOuf, lOOOuf
10 , 000 ut

A tough and dependable multimeter designed
tor true one-hand operation. It has a 3 3/4
digit (4000 count) display, as well as auto
and manual ranging. With AC/DC voltage
measurements (to 600 volts), continuity
beeper, Ohms & diode tester, digital display,
and overload protection. The Fluke 10,
a new generation in speed, versatility
and value.

Cat Q 1611

2 YEAR WARRANTY!

Specifications

DCV: 4000mV, 4V, 40V, 400V 600V
Accuracy: (1.5% +2 for 4000mV & 4V
ranges) (1.5% +1 for 40V, 400V & 600V
ranges)

ACV: 4000mV, 4V, 40V, 400V, 600V
Resistance: 400 Ohm, 4K Ohm, 40K Ohm
400K Ohm, 4M Ohm, 40M Ohm

$ 109i

LEADS AND CLIPS

Industrial Test Lead Set

Silicon insulated test leads (63" long). With
shrouded right-angle connectors, interchangeable
stainless steel test probes and safety * —
alligator clips. 5 / O 95

Cat Q-1652

Alligator Clips

Set of two black and two red slip-on clips for

Right-Angle Test Leads

Shrouded input plugs which will not pull out of
meter during use. Single piece construction.

1 metre long. aqc

CatQ-1650

right-angle test leads
CatQ-1660

$ 12

Fluke 10 & 12 Holster

Snap your meter into this yellow holster
and it will absorb shocks and protect it
against damage. With tilt stand and a
moulded hanger loop which can be used as
a probe holder < A m 95
Cat Q-1614 Z4

Fluke 10 & 12 Softcase

The best way to keep your Fluke series 10
meter sate and organised. There's room for
leads and small accessories as well a 95
Cat Q-1616

Deluxe Test Lead Kit

Everything in a handy soft carry pouch. Comes with
interchangeable tips - 2 alligator clips, 2 spade
lugs, 1 retractable hook tip & 2 standard pointed
tips. Includes shrouded banana plugs. $cr f %95
CatQ-1658 OY

High Voltage
Probe

*199

Measuring high voltages made easy
and sate. Division ratio is 1000:1.
Measures up to 40kV or 28kV RMS AC. Has
1 OOOMohm input resistance.

CatQ-1690

Also Avalialable!....

70 SERIES II FLUKE MULTIMETERS

The all new Series II Fluke professional quality multimeters give you
better value, better performance and more features than ever before.
All of the 70 Series' meters now have 'Touch Hold', Diode Test,
Continuity beeper. Automatic Self Test, Sleeper Function and
exceptionally long battery life as standard features.

Fluke 73 Series II

Cat Q-1603

Fluke 75 Series II

Cat Q-1605

Fluke 77 Series II

Cat Q-1607

MAJOR DICK SMITH ELECTRONICS AUTHORISED STOCKISTS:

■■■■■■■

EXCLUSIVE

Shortwave Listeners

Guidebook Harry Helms

With Cassette Player!

All-Band World Receiver

Open your ears to the world with the stunning Sangean ATS-8180S.
This fantastic receiver covers Longwave and continuous shortwave
frequencies from 1.62 to 30MHz and local AM/FM stations (FM stereo
with optional headphones). What's more, with an inbuilt BFO (beat
frequency oscillator) it can receive many HF SSB transmissions
including marine, aircraft, amateur and commercial broadcasts. An
inbuilt tape deck even allows you to play your favourite tapes and pre¬
set it to record broadcasts. Top teatures include five-way tuning, 45
station memories, a full function digital display, dual time and alarm
clock. A dual conversion receiver design offers switchable filters and an
adjustable RF gain control to provide optimum reception. It's simply
brilliant! . ^

Cat D-2842 5 r OO

Learn how to tap into the
exciting and 'live' the
world of shortwave! This
valuable book tells you
how to get the best
programs, news and
broadcasts from around
the world. As well, there's
tips on choosing the right
antenna, conditions
affecting reception,
international & domestic
broadcasting and more.
Cat B- 2040

Passport To World Band
Radio 1992

A valuable guide on how
to get started with your
shortwave receiver. It's
packed with useful
information, with everything
from what's on, to the
best (& worst) SW radios.

If you've just discovered
shortwave radio, are just
starting out, or want to keep
up with the latest world
changes, this book is a
definite must-have!

Cat B-2050

World R adio TV Handbook

1998 EDITION ^92

One of the most sought
after books among
shortwave enthusiasts.
With up to date and
complete listings of
international radio and
TV stations. Provides
frequencies, addresses,
call signs, ID s... you
name it.

B-2092 $^£>95

WORL

RADIO

Easy To Use

Easy Etch Engraver

A quick and effective way to make sure your tools
don't get mixed up with others This reliable
engraver lets you quickly mark tools, stereo
equipment and household valuables with a
permanent identification or serial number. It's
easy to handle and has steel bits so you can
engrave on metal, plastic, wood and most
materials. Complete with 12Vplug pack and long
cord.

Cat T 4753

Quick and Easy!

Heat ’n
Strip Gun

Cut your work time by halt!

This handy tool is ideal for
heatshrink work, removing old
paint, removing vinyl tiles,
loosening rusted or over-tightened nuts, drying...
and hundreds of other uses. It's lightweight,
mains operated and has a dual temperature range
(400 & 600°C). A M _

Cat T 4845 I 95

Ideal for PCB work!

Super Tool

A must tor any hobbyist or enthusiast 1 This
extremely high quality tool is perfect for PCB
and other precise work. It sands, polishes, drills
engraves, and mills What's more, it comes
with a wire brush, milling cutters, grinding wheel,
high speed drills, chuck collets, eraser sticks
and mains adaptor Complete with handy,
go-anywhere plastic case n
Cat T-4754 v # OVO

DS XPRESS PHONE & MAILORDER SERVICE

Outside Sydney (FREE Call) 008 22 6610 Sydney And Enquiries - 888 2105

FAX: (02) 805 1986 or write to DS XPRESS, PO BOX 321 N/RVDE NSW 211?

All Major Credit Cards Accepted. O/Nite Courier Available.

24 HOUR DESPATCH OF ALL ORDERS

DiCK^SMITH

ELECTRONICS

M'oh! irn M 3 MT5%?narn 1 ona V 794 0 9377 n - E^tBhghton 592 Y 366 -Essend'on 379 7444* Footscray 689 2055 • Frankston 783 9144* Geelong 232 711 • Melbourne City
aQQ Fiiyat-mm v Rofis ?46 Bourke St 639 0396 • Richmond 428 1614 • Ringwood 879 5336 • Spnngvale 547 0522 QLD • Booval 282 6200 • Brisbane City 229 9377
*233™a,ms31151^"ata 359 8255 • Rockhampton 27 9644 • Southport 32 9033 . Toowoomba 38 4300 .Townsville

72 5722 • Underwood 341 0844 • SA • Adelaide City 232 1 200 • Beverley 347 1900 • Elizabeth 255 6099 • Enfield 260 6088 • St. Marys 277 WA * ^ ann ' n § t0 £
451^8666 • Fremantle 335 9733 • Perth City 481 3261 • Midland 250 1460 • Northbridge 328 6944 TAS • Hobart 31 0800 • Launceston 344 555 MT • Stuart Park

81 1977

B1374

Construction Project:

VHF/UHF SPECTRUM
ANALYSER ADAPTER • 2

As promised last month, here are the constructional details for our new spectrum analyser project,
plus information on how it is set up and used. As most of the parts mount on a PC board, construc¬
tion is quite straightforward.

by JIM ROWE

The analyser is housed in a standard
compact plastic instrument case, of the
type having a ‘U’-shaped top and bottom,
and removable front and rear panels. The
nominal width and depth are 200mm and
160mm respectively, and the front panel
artwork has been designed to be com¬
patible with the two slightly different
cases currently available: that from Jaycar
Electronics, with a height of 70mm (Cat.

No. HB-5912), and that from Dick Smith
Electronics with a height of 65mm (Cat.
No. H-2505).

Inside the case, most of the components
and circuitry are supported by a single¬
sided PC board. This measures 166 x
114mm, and is coded 92vsa9. The only
components not mounted on the PCB are
the various controls and connectors
mounted on the front panel, and the con¬

nectors, mains fiiseholder and power
transformer which are mounted on the
rear panel. More accurately, the trans¬
former is mounted on a small earthed
metal plate, which is in turn mounted on
the rear panel — to ensure adequate
safety if the transformer ever overheats.
This will be discussed further later.

The location of all of the parts mounted
on the PCB should be fairly clear from

A close up view inside the case, showing the front part of the PCB assembly and the wiring to the front panel controls and
connectors. The tuner module is attached to the board by soldering to four PCB pins — one at each corner.

ELECTRONICS Australia, October 1992

the PCB overlay diagram and the
photographs. Note that the varicap tuner
module is mounted on its side, with PCB
pins used both to attach the case to the
board (by soldering to the case), and to
make most of the actual connections to
the tuner. The only exception is the RF
input, which connects to the rear of the
front-panel BNC socket via a short length
of co-axial cable and an RCA plug.

By the way, the reason for mounting the
tuner module on its side (when it is
designed to mount vertically, with its con¬
nector pins passing directly through the
PCB) is to ensure compatibility with dif¬
ferent tuner modules. These can vary in
terms of width and mounting lug spacing,
so by mounting the module on its side, we
can accommodate the variations more
conveniently. For example the earlier
TUMUF4EA-706 module can be used in¬
stead of the -721 module specified, if you
have one.

Construction

The logical way to begin construction
of the analyser is by .assembling every¬
thing that mounts on the PCB. Here the
first step is to fit the 52 PCB pins, which
are used for making many of the off-
board connections as well as attaching the
tuner module.

You can see where most of the PCB
pins go from the overlay diagram and the
photo’s — virtually all of them are either
along the front or back edges of the board,
or around the tuner’s location. All pins
pass through the board from the top (com¬
ponent) side, and are soldered to the pad
underneath, with their longer end above
the board (measured from die ‘bulge’).

The next step is to mount the tuner
module, on its side and inside the PCB
pins that are located at each comer. You
should find that when you do this, the
tuner’s own connection pins will all line
up with the row of PCB pins, ready to be
soldered together.

However before you do this, carefully
bend the ‘comer’ pins (with a pair of
needle-nosed pliers) until they are all
nicely nudging the ends of the
module, when it is in the correct loca¬
tion. You’ll probably have to remove and
replace the module a few times, to bend
these pins conveniently and test the
result Then when everything seems to
line up nicely, solder the four comer
pins to the module case to hold it in posi¬
tion, and finally solder the various con¬
nection pin junctions.

At this stage I suggest you fit all of the
small passive components, with the resis¬
tors first, then the metallised polyester,

ceramic and monolithic capacitors. Take
care with virtually all of these capacitors
to mount them as close as possible to the
board, without straining their pigtails, and
then to solder them quickly and carefully
to avoid overheating.

Before proceeding further, mount the
two PCB links so that you don’t foiget
them later. One is next to R53, and the
other is near R3. Both are visible in the
PCB overlay.

The electrolytic and TAG tantalum
capacitors would be next, taking care to
mount all of these with the correct
polarity as shown on the PCB overlay.
Then fit the signal, rectifier and zener
diodes, again taking care with their
polarity.

Next follow the trimpots RV4 and RV6,
the discrete transistors, the ceramic filters
FI and F2, the 47uH RF choke and the
crystal XL Both the filters and crystal
should be mounted as close to the board
as possible, without straining their pins,
and again soldered quickly and carefully
to avoid overheating.

The next step is to wind the coils LI,
L2 and L3. These are all wound on readi¬
ly available 4.85mm formers, which have
mating 6-pin bases and shield cans (DSE
Cat No. R-5020, R-5010 and R- 5000, or
similar). IF transformer LI is fitted with

In this second close up , looking towards the rear, we see most of the rest of the board assembly along with the rear panel
and its components. Note that the power transformer is mounted on a small square of aluminium sheet.

ELECTRONICS Australia, October 1992

VHF/UHF Spectrum Analyser Adapter - 2

an F29 ferrite slug (DSE Cat No. R-
5030), while L2 and L3 are fitted with
FI 6 slugs (DSE Cat No. R-5025). Both
windings of LI are wound using 0.5mm
enamelled copper wire, which is also used
for L2; however L3 is wound using
0.25mm enamelled wire.

Winding details for all three coils are
shown in the small box. Make sure you
terminate the coil windings on the pins
shown, as the PCB pattern is designed to
match these connections. When the coils
have been wound and checked, they can
then be mounted on the PCB. Make sure
you orientate them correctly, and then
push the base pins through the PCB as far
as they will comfortably go.

Then solder the pins to the PCB pads,
and carefully clip off the excess pin
ends. Then fit the shield cans, soldering
their attachment/earthing pins to the

earth copper and again clipping off the
excess. Finally fit the threaded slugs,
preferably slipping a 25mm length of fine
rubber thread into the former first, to
act as a ‘brake* against slug movement
due to vibration.

The last step in completing the PCB as¬
sembly is to fit the ICs. These all mount
directly on the board, although sockets
could be used for U4, U5, U6 and U7 if
you wish.

Do NOT attempt to use a socket for IF
amplifier chip Ul, however — this chip
needs to be mounted as close as possible
to the board, with minimum lead lengths,
to ensure stable operation.

Don’t forget regulator IC’s U2, U3 and
U8. These all mount vertically, and are
orientated as indicated in the overlay
diagram — which also shows the orienta¬
tions for all of the other IC’s.

With the PCB now fully assembled,
you can turn your attention to drilling
the holes in the front panel, to accept the
various connectors, switches and pots.
You should be able to use a photo
copy of the front panel artwork to locate
the holes correctly, but it is usually ad¬
visable to use the components themselves
as a guide to the exact hole sizes — there
are quite a few different sizes in current
use, when it comes to pot and switch
mounting bushes.

You may also wish to drill ‘blind’
holes from the rear of the panel, to accept
the locating/anchor spigots on some of
the controls.

After drilling and reaming the various
holes to size, you can then fit the
Dynamark (formerly Scotchcal) front
dress plate, if you’re using one, and cut
holes in this to match the main con-

Here is a general view looking into the analyser's case, showing where everything goes. Almost all of the circuitry and
components mount on a single PC board.

ELECTRONICS Australia, October 1992

trol and connector holes. Then the various
parts can be mounted — after cutting
the pot and switch spindles to length,
of course. The final step is to fit the con¬
trol knobs.

The rear panel assembly is next
prepared, in a similar way to the front
panel. Here there are a smaller number of
holes, but two of these are relatively
large: that for the captive EEC mains plug,
which is rectangular, and that for the
mains fuseholder which is round.

These are best prepared by drilling a
series of small holes inside a marked-out
area, cutting between these with a sharp
knife, and filing the holes carefully to
their final size.

As mentioned earlier, the mains trans¬
former is firmly mounted on a 55mm
square of 1mm-thick aluminium sheet,
using 3mm countersink-head machine
screws, nuts, flat washers and ‘star’ lock¬
ing washers. A solder lug is fitted under¬
neath one of the mounting nuts, to allow a
wire to be connected to the earth lug of
the IEC plug.

The complete assembly is then
mounted on the plastic rear panel, with
the transformer orientated so that its 240V
primary leads will exit from the bottom
when the panel is fitted into the case,
using a pair of standard 3mm screws, nuts
and lock washers.

When the plug, fuseholder and trans¬
former assembly are mounted on the
panel, the transformer primary leads can
then be connected to the ‘N’ lug on the
IEC plug, and the fuseholder lug nearest
the panel.

The other fuseholder lug is then con¬
nected to the the ‘A’ lug of the IEC plug.
Note that all four of these mains con¬
nections should be carefully made, and
provision also made for insulating them
after soldering using either varnished
cambric sleeving or ‘heatshrink’ sleeving
— to ensure that they can’t be touched
inadvertently.

It’s also advisable to use small nylon
‘cable ties’ to bind together the two ‘live’
leads connecting to the EEC plug lugs, and
also the transformer primary and secon¬
dary leads. This helps prevent accidental
contact, should any one wire break away
from its soldered joint.

Don’t forget to fit the earthing wire
from the transformer solder lug to the EEC
plug’s ‘E’ lug, too. This should be in
mains-type wire, with the usual green or
green/yellow striped insulation.

The RCA connectors can also be fitted
to the far end of the rear panel, to com¬
plete this assembly. Note that although
bleed resistor R60 is visible in the
photographs wired directly across the
back of the audio output socket, this resis¬

tor is probably best mounted on the back
of S3b, the sweep width switch — as
shown in the wiring diagram.

You should now be ready for the final
step in assembly of the analyser mount¬
ing the PCB in the lower half of the case,
and making all of the connections be¬
tween it and the front and rear panel as¬
semblies. This is done most conveniently
by laying the panels ‘face down’ in front
of their final positions, and wiring in the
various internal leads in a methodical
fashion, using the wiring diagram and
photographs as a guide.

Note that the leads to all of the signal
connectors are made in light-duty coaxial
cable, while most of the rest of the wiring
can be done using ‘rainbow’ colour-coded
ribbon cable separated into appropriate
conductor groups.

The 12.6V AC secondary leads from
the power transformer connect directly to
the input pins at the rear of the PCB. You
may wish to shorten these leads a little, to
keep them from draping over the board
circuitry when the unit is fully assembled.

And once all of the connections
have been made, you can slot the front
and rear panels into the lower case.
You’ll then be ready for the next phase:
firing it up.

Testing and adjustment

Before applying the power, set both of
the preset trimpot RV4 and RV6 to their
fully anticlockwise positions, as viewed
from above. Also have a DMM handy, set
to say the 20V DC range, and with its
negative test lead connected to the earthy
side of one of the BNC connectors, ready
to check the supply voltages.

Now apply the power, and quickly
check the voltage at the input pin of 12V
regulator U8 — the pin nearest C49. This
should measure about +17.5V. Now
quickly check the voltage at the output
pin of the same IC, which should measure
+12V, and also the output voltages from
U2 and U3. These should read close to
+9V and +6.2V respectively.

If any of these voltages are well away
from the nominal figures, and/or any of
the regulator IC’s are getting noticeably
hot, switch off the power immediately
and check for wiring errors. The odds are
you’ve connected something in the wrong
way around!

All being well, however, change your
DMM to the next higher DC volts range
and check the voltage at pin 11 or pin 12
of U7. This should read about +32V, if the
voltage doubling rectifier diodes and
capacitors are fitted to the PCB correctly.

The next step is to measure the voltage
at pin 4 of U6, or on the rotor lug of
sweep rate pot RV2. This will probably

read around +25V or so. With the meter
still connected, now is the time to slowly
turn trimpot RV6 clockwise, using a small
screwdriver, until the DMM reading rises
to +28V. Your tuning/sweep voltage supp¬
ly rail will now be set correctly.

All being well so far, you can hook
your ’scope up to the analyser adapter,
connecting the Y output to the scope’s Y
input and the X output to the scope’s X
input. Or if your scope doesn’t have an X
input, connect the analyser’s rear ‘Trig
Out’ to the scope’s external trigger input
— or even to its second Y input, if it
doesn’t have an external trigger input. Set
the scope’s Y input gain to lV/div, or
thereabouts.

There will probably be very little to
see on the main Y input, at this stage,
except perhaps a DC level of a few
hundred millivolts. But you should be
able to get plenty of X deflection, if
you’re in X-Y mode, from the analyser’s
8 V p-p sweep sawtooth — or alternative¬
ly good time-base locking, from its 11V
p-p trigger pulses.

The timebase should be set to around
2ms/div, if you are using triggering, with
the analyser’s Sweep Rate pot set to about
mid range. The presence of trigger pulses
and a sweep sawtooth indicates that the
analyser’s sweep oscillator circuitry is
working correctly, of course.

Now you should be ready for the
analyser’s alignment. For this, you should
ideally have some kind of RF signal gen¬
erator, or perhaps a small transmit¬
ter/transceiver capable of generating a
signal in one of the analyser’s three fre¬
quency bands. If you use a transmitter or
transceiver, you’ll also need a dummy
load to feed most of its output into (the
analyser will probably detect enough
leakage to let you do the alignment).

If all else fails, you can even
perform the alignment reasonably well
using signals from a suitable TV
antenna — providing you’re not in an
outer fringe area.

With a signal generator or a TV anten¬
na, the analyser’s RF input can be con¬
nected direcdy, using a suitable length of
coaxial cable. The signal generator should
be set to a frequency near the middle of
one of the analyser’s bands (say 75MHz,
170MHz or 600MHz), and to produce an
output of say 40-50uV.

At this stage the analyser’s band switch
should be set to the band you’ll be align¬
ing it on, its RF gain control fully clock¬
wise, both centre frequency controls to
about mid range, and the Sweep Width
switch to ‘Max*. The Sweep Rate pot can
be left at mid range, and the Audio
Muting pot fully anticlockwise. The
Bandwidth switch can be set to ‘Low’.

ELECTRONICS Australia, October 1992

VHF/UHF Spectrum Analyser Adapter - 2

Coil winding details

(Former ond pins
viewed from obove)

Ll (F29 slug):

Primory 1 turn 0.5mm ECW,
between pins 1 and 2
Secondary 8 turns 0.5mm ECW,
between pins 5 and 6

L2 (FI6 slug):

8 turns 0.5mm ECW,
between pins 5 and 6

L3 (FI6 slug):

20 turns 0.25mm ECW,
between pins 1 and 2

Above are the winding details for the IF transformer LI, the
crystal oscillator coil L2 and the quadrature sound coil L3.
All three coils are wound on miniature (4.85mm) formers,
fitted to 6-pin bases. The various windings are terminated
on specific pins, as shown.

Above: The rear panel of the analyser. At upper left are the
captive I EC mains plug and fuse holder, while at far right are
the audio output (top) and trigger output connectors. The
two additional screws visible are used to attach the power
transformer mounting plate to the plastic rear panel.

Right: The front panel artwork for the analyser, reproduced
here actual size for those who wish to make their own
Dynamark front panel. The small lines at each end indicate
where the panel is trimmed if you are housing the analyser
in the case sold by Dick Smith Electronics — which is a few
millimetres shorter than that sold by Jay car Electronics and
others.

By now, you should be able to see
at least one ‘blip’ on the scope’s dis¬
play, if you’re using a generator or a
transmitter/transceiver, or perhaps quite
a few if you’re using a TV antenna.
In the latter case you might even have to
turn down the RF Gain pot a little, to
reduce the clutter.

The idea now is to use the Centre Fre¬
quency controls to move the single blip
(or a suitably prominent one, with a TV
antenna), to the very centre of the scope
trace. Then reduce the Sweep Width one
step (to ‘zoom’ in), and if necessary re¬
centre it again. Then reduce the Sweep
Width once more, by which time you

should have the blip quite clearly visible
on a relatively uncluttered trace. If you
have difficulty identifying the blip, try
varying the signal generator’s frequency
— which will make the blip move along.
Or turn your transmitter on and off, which
will make it ‘come and go’.

What if there’s still no blip evident at

ELECTRONICS Australia, October 1992

TRIG OUT

No prizes for guessing that this is the wiring diagram for the analyser, showing all of the connections between the
PC board and the various controls and other off-board components. Don’t worry if you can’t make out the
components on the board itself—these are more clearly shown in the PCB overlay diagram.

ELECTRONICS Australia, October 1992

VHF/UHF Spectrum Analyser Adapter - 2

all? This will probably be due to the crys¬
tal oscillator coil L2 being way off, which
can prevent the oscillator from operating
— or allow the crystal to oscillate on its
fundamental, instead of the correct third
harmonic. So try adjusting the slug in L2,
until a blip appears.

At this stage the peak of the blip should
be about half screen height. If it’s higher
than this, turn down the analyser’s RF
gain control until it is; if it’s too small,
either turn up the gain or increase the gen¬
erator’s output a little.

Now try adjusting the slug in IF trans¬
former LI. It should be possible to ‘peak’
this — that is, find the slug position where
the blip’s height reaches a maximum. If
the slug was well away from this position
to start with, the blip’s height may grow
quite a lot as you approach the peak, so if
this happens keep turning down either the
analyser’s RF gain, or the generator’s out¬
put, to keep the blip height roughly half of
the screen. This prevents overloading ef¬
fects, and ensures that you can easily see
the effects of your adjustments.

When LI is nicely peaked, try adjusting

the slug in oscillator coil L2. Again there
should be a setting of the slug which
causes a peak in the blip amplitude, and
that’s where the slug should be set.

There’s also a tiny slug in the tuner
module’s own IF output coil, which you
can adjust for a peak as well. The slug is
accessed via a hole in the tuner’s case,
just near the IF output pin (the one nearest
LI). But the slug is very small, so you’ll
need to use a very small alignment tool
and be very careful. Its tuning is quite
broad, but a little tweaking can often
produce a worthwhile improvement.

By the way, all of the analyser’s coil
slugs should of course be adjusted using a
plastic alignment tool or a suitably filed
plastic knitting needle — don’t use a
screwdriver, as this will upset coil opera¬
tion. Also make sure that the alignment
tool’s tip correctly fits the slot in each slug
— the ferrite material is quite brittle, and
can be easily broken.

I actually had to make a special and
very small tool to align the tuner’s output
coil, because of its very tiny slug. This
was made from a discarded plastic

crochet needle, but cutting off the hook
and then carefully filing the end into a
tiny ‘blade’.

By now your analyser’s main align¬
ment is essentially complete; you can
now adjust detector coil L3 for the best
audio output when the analyser is being
used as an FM receiver.

To do this, you’ll need to connect the
analyser’s rear audio output socket to a
suitable small audio amplifier, to allow
you to hear the output (shortly). You’ll
also need to remove the signal generator’s
output, if you’ve been using one, or turn
off the transmitter if you’ve been using
that approach. Then connect either a TV
antenna, or some other antenna which can
provide a suitable source of reasonably
wideband FM signals, to the RF input

Suitable signals are the main sound car¬
rier from a TV station, or the signal from
an FM broadcast station — so the next
step is to manipulate the centre frequency
and sweep width controls until you have
identified such a signal, and centred its
‘blip’ on the scope trace.

It shouldn’t be difficult to find a

Here is the PCB overlay diagram, showing where everything goes on the board. Note that many of the components
associated with the IF amplifier chip ill need to be mounted as close as possible to the board itself, to minimise lead length.
The NE605N chip must also be soldered directly into the board, to ensure stable operation. Header block J1 is not used.

suitable FM broadcast signal, near the top
of the analyser’s 50-108MHz band, or a
TV sound signal on any of the bands.
You’ll soon learn to identify TV station
signals, from their appearance on the
trace: a main single blip for the vision
carrier, plus two closely-spaced blips for
the stereo sound carriers, 5.5MHz higher
in frequency (i.e., to the right, on the
scope display). Often there’s another
small blip corresponding to the colour
subcarrier, at about 75% of the distance
between the vision and picture carriers; a
typical TV station’s signal group was
shown in the lower left-hand picture on
page 67 of the September article.

Once you’ve identified a reasonably
strong FM sound carrier, the idea is again
to centre it on the scope trace, and ‘zoom
in’ on it step by step, by switching to
lower settings of the sweep width control.
Each time you switch to a lower setting,
you’ll generally need to adjust the centre
frequency pot slightly, to keep it in the
centre. Then finally, when you have it
nicely centred and ‘expanded’ in the
lowest of the five sweep width ranges,
switch the Sweep Width switch to its final
‘Off’ position.

You should now be able to hear the

demodulated FM audio, although it may
well be a little weak, noisy and distorted.
If you can’t hear anything, check that
your Audio Muting pot is fully anticlock¬
wise (or fully clockwise, if you’ve wired
it with the connections to the ends
transposed!). You may also need to adjust
the gain of the audio amplifier, to achieve
a reasonable audio level.

You’ll notice that the ‘blip’ has ap¬
parently disappeared from the scope
screen, but is replaced by a horizontal
line. This is actually the ‘prak’ of the blip,
spread to the full width of the horizontal
sweep. If you try adjusting the Centre
Frequency pot slightly, you’ll find that the
line moves up and down — in this ‘FM
Receiver’ mode, the scope can be used as
an S meter.

Carefully set the Centre Frequency pot
so that the line moves to its maximum
vertical position (peaking the signal
tuning), and if necessary adjust the
analyser’s RF Gain pot so that the line’s
position is comfortably above the centre
of the screen. Then try adjusting the slug
in detector coil L3.

The tuning of L3 is fairly broad, but
you should be able to find a position of
the slug where the audio output is loudest

and clearest — with virtually no distor¬
tion, and very little if any noise. This is
the correct setting.

The final step in adjusting your
analyser is to set trimpot RV4 to its cor¬
rect value. You may recall that this pot is
used to set the gain of the sweep output
stage, for optimum operation.

To make this adjustment, disconnect
the analyser’s Y output from the scope,
and re-fit its usual test probe. Then set the
scope’s Y input for a sensitivity of say
5V/div (taking into account the probe at¬
tenuation), and attach the probe tip to
either the tuning voltage pin of the
analyser’s tuner module (pin 7, ‘Vc’), or
the end of resistor R29 nearest to the front
panel. You will now be able to view the
tuning/sweep voltage applied to the tuner.

Now set the Centre Frequency switch
and pot to the middle of their overall
range — say with the switch on position 3
(from anticlockwise) and the pot fully
clockwise. With the Sweep Width switch
set to the ‘Off’ position, you should see a
horizontal line about halfway up the
scope screen.

If you switch the Sweep Width control
to its next position, the line should be¬
come a linear ramp — sloping upward to

And finally , here is the PCB pattern for the analyser , reproduced actual size as usual , for those who wish to make their own
board.

ELECTRONICS Australia, October 1992

VHF/UHF Spectrum Analyser Adapter - 2

PARTS LIST

Resistors

(All 1/4W 5% unless specified)

R1, R43, R44, R50, R59
4.7k

R2,R3,R52,R54

10k

R4.R5.R7 430 ohms 1%

R6 510 ohms 1%

R8.R9 820 ohms

R10 l R11,R12,R13 t R14,R15 i R16,R22
3.9k

R17,R20,R60

22k

R18 39k

R19 27k

R21.R24 2.2k

R23 2.7k

R25 220 ohms

R26 I R37,R49,R53,R56
Ik

R27, R28, R33, R57, R58
100k

R29, R30, R31, R32, R61
220k

R34 33k

R35,R36,R38,R55
47k

R39.R42 1.8k

R40 10 ohms

R41.R45 6.8k

R46 470 ohms

R47.R48 180k

R51 1.5k

RV1.RV3 10k linear pot
RV2.RV5 20k linear pot
RV4 1M lin mini trimpot
RV6 Ik lin mini trimpot

Capacitors

01,02,03,05,06,09,010,039
10nF monolithic
04 47uF NPO ceramic

07,08,011,012,020,021,023,025
0.1 uF monolithic
013 2.2pF NPO ceramic

014,015,022,026,030,031,032,040,048
2.2uF 25VW TAG tantalum
016,027,047

IOOuF 16VW RB electrolytic
017 330pF NPO ceramic

018,019,024,037

lOOpF NPO ceramic
028 68pF NPO ceramic

029 470pF NPO ceramic

033 22uF 16VW TAG tantalum

C34 6.8uF 35VW TAG tantalum

035 4.7uF 35VW TAG tantalum

036 15uF 16VW TAG tantalum

038,042,049,050,051

33uF 35VW RB electrolytic
041 IOOuF 25VW RB electrolytic

043 2200uF 25VW RB electrolytic

044 1 nF 50VW metallised polyester

045,046 0.1 uF 50VW metallised

polyester

Semiconductors

D1,D2,D3,D10

1N4148 silicon signal diode

D4,D5,D6,D7,D8,D9

1N4001 1A/100V silicon diode

BC558 silicon PNP transistor

BC548 silicon NPN transistor

NE605N FM IF amp/detector

U2.U3

7805 5V regulator

555 timer

U5,U6

LM324 quad op amp

LM723 adj. voltage regulator

7812 12V regulator

4.7V 400m W zener diode

Z2.Z3

5.1V 400mW zener diode

Miscellaneous

26.175MHz crystal (see text)

F1.F2

10.7MHz ceramic filter

L1,L2,L3

(see text)

Coil, wound on 4.85mm former

with 6-pin base, shield can and
slug (see winding data)

VHF/UHF tuner module (Murata
TUMUF4EA-721)

RFC

47uH RF choke

Three pole, 3 position
rotary switch

S2.S3

Two pole, 6 position
rotary switch

SPDT miniature toggle switch

12.6V/150mA power transformer

1 x plastic instrument case,

200 x 160 x 70mm (see text);

1 x I EC mains input plug, panel mounting;

1 x 3AG fuseholder, panel mounting

screw-in type with 500mA fuse;
3 x BNC sockets, single-hole

panel mounting type;

2 x RCA audio sockets, single-hole

panel mounting type;

1 x RCA plug, compact type with
short pin (see text);

7 x small instrument knobs;

52 x PCB pins;
light 75-ohm coaxial cable;
shielded audio cable;
hookup wire;

square of 1mm aluminium sheet,

55mm square;

3mm machine screws, nuts and
locking washers;

solder, etc.

the right, by a small amount. Switch¬
ing to the higher Sweep Width positions
should increase the slope of the ramp,
until in the maximum sweep width setting
it will reach maximum slope, and probab¬
ly also develop horizontal sections at its
ends — due to overswing of the sweep
output stage.

Now, using a small screwdriver,
slowly turn trimpot RV4 clockwise. The
slope of the ramp will gradually reduce,
and as it does the horizontal segments
at top right and lower left will shrink. The
centre frequency will also change slighdy,
so you will need to adjust the centre fre¬
quency pot as you go, to keep the ramp
symmetrical both horizontally and verti¬
cally on the screen.

Keep turning up RV4 until the horizon¬
tal segments at the ends of the ramp have
just disappeared, leaving a diagonal ramp
whose peak-to-peak amplitude is achiev¬
ing the maximum possible linear swing.
This is the correct setting for RV4, and
your spectrum analyser is now fully
aligned and ready for use.

Troubleshooting

Apart from problems due to wiring er¬
rors and accidental swapping of com¬
ponents or fitting them into the PCB with
the wrong orientation, there’s not a lot
that is likely to go wrong with the
analyser, assuming you’ve followed the
foregoing description carefully. In any
case many of the possible pitfalls have
already been mentioned, along the way.

If the DC voltages all check out cor¬
rectly, and there’s a X-output sawtooth
and/or trigger pulses, but otherwise the
analyser seems ‘dead’, with no blips
visible on the scope display, the most
likely cause is that you have a low activity
quartz crystal, which is refusing to oscil¬
late.

In all but the most stubborn of cases
this can be remedied by connecting a 33k,
27k or 22k resistor from pin 3 of U1
(NE605N) to ground. This increases the
quiescent current in the chip’s internal os¬
cillator transistor, and gives it a little more
gain, to persuade the crystal to oscillate.

Note that this external emitter resistor
should not be reduced below 22k. If the
crystal still refuses to oscillate (which you
can monitor using the scope probe ap¬
plied to pin 4), you probably have a faulty
crystal and it’s better to replace it.

The external resistor is only likely
to be needed with low activity crystals,
by the way. The chip’s internal cir¬
cuitry is quite adequate to oscillate with
all normal crystals.

Using the analyser

You’ve probably gained at least a
general idea of how the analyser is used
from the discussion this far.

The bandswitch is used to set the band
to be examined, while the centre frequen¬
cy controls allow you to bring virtually
any frequency in each band to the centre
of the scope trace, for examination.

The Sweep Width switch allows you
to examine the full band initially, if
you wish, and then zoom in to any par¬

ticular signal or band segment of inter¬
est. The RF gain control allows you to
achieve maximum gain for very weak
signals, or lower it to prevent overload
and generation of spurious products with
very strong signals.

The purpose of the Sweep Rate pot is to
allow fast sweeping (with lower visible
flicker) when this is possible.

However as this can cause some distor¬
tion of narrow-band signals, due to the
analyser’s modest IF selectivity, the pot

ELECTRONICS Australia, October 1992

also allows you to slow down the sweep¬
ing when required. Often the pot can be
left in the centre of its range.

The Bandwidth switch allow you to in¬
troduce additional filtering when you’re
looking at signals under noisy conditions,
making them easier to examine. However
in the Tow’ position it can cause the ap¬
parent amplitude of signals to be
reduced, especially when you’re using a
high sweep rate. Hence the ‘High’ posi¬
tion, to allow more accurate examination
of signals when conditions allow.

And finally there’s the Audio
Muting control, which only operates
when you’re using the analyser in its ‘FM
receiver’ mode.

Here the control acts very much like a
traditional ‘squelch’ control: in the fully
anticlockwise position, virtually all sig¬
nals are heard, but as you turn the control
up, only stronger and stronger signals are
able to surmount the gating barrier. This
allows you to reduce listening fatigue by
gating off the noise between signals.

An important point to remember, when
you’re using the analyser for spectrum
analysis, is that the maximum sweep
width you can use at any time depends
upon the centre frequency setting. The
full sweep setting will only give an undis¬
torted sweep when you have the centre

frequency controls set for the middle of
each band; as you adjust the centre fre¬
quency controls to move further away
from the mid-band setting, the sweep
width will need to be reduced to match —
or you’ll get some strange effects, as the
sweep output circuitry ‘hits its limits’.

Generally this shows up on the
scope display as a ‘plateau’ or ‘dead
area’ on one end of the trace, where
the X sawtooth is still providing sweep,
but the analyser’s tuning is not able to
follow any further.

It’s an effect that tends to happen
even with the most elaborate lab¬
oratory analysers, and after using the in¬
strument for a while you’ll soon learn
both to recognise the symptoms and ad¬
just the controls to remove or at least min¬
imise them.

A final point. When you switch off the
sweep to listen to the modulation on a
signal of interest, the analyser effectively
becomes an FM receiver — with the
centre frequency switch and pot as its
tuning controls.

Up on the UHF band the tuning does
become a little critical, but with care it’s
quite possible to tune in quite narrow-
band FM signals — using the scope ‘S
meter’ as a guide.

With a sensitivity of better than one

microvolt, the analyser is actually quite a
useful little VHF/UHF receiver in this
mode. Even though it has a reasonably
broad selectivity (170kHz), you can even
listen to quite narrow-band signals, if
your external audio amplifier has a
reasonable amount of gain.

Its main shortcoming is that if there
are a number of narrow-band signals
very close together (i.e., all within the
170kFlz passband), you’ll tend to heaf
them all together.

As mentioned in the first article, it
would be possible to improve the
selectivity of the instrument both as an
analyser and as a receiver, by sub¬
stituting a 10.7MHz crystal filter for the
first ceramic IF filter FI. I’ll leave
this for the more adventurous and
well-heeled contractors...

Now for the obvious question: could
the analyser somehow be used to look at
signals below 50MHz, or in the ‘gaps’ be¬
tween the current bands?

That’s the next step, and I’m currently
working on a suitable ‘up-converter’
project to do the job, in between other
projects. If there’s sufficient interest. I’ll
try to finish it and publish the details.

In the meantime, I hope you find the
present spectrum analyser adapter a use¬
ful addition to your workbench. ❖

■ ■

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The Australian Electronics Development Centre (AEDC), now in Its third year of
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AEDC

READER INFO NO. 21

READER INFO NO. 22

ELECTRONICS Australia, October 1992

AUTOMOTIVE

ELECTRONICS

Engine basics - 4

Last month, we discussed the ignition system. This time we’ll conclude our brush-up on engine
basics with a look at the intake, emission/pollution control and electrical systems. With the basics
out of the way, I’ll be able to devote future columns to my favourite subject: the practicalities of
automotive electronics, and what you need to know to fix the car.

First of all, let’s look at the intake
system. To better understand this sys¬
tem, it is divided into two parts: the air
intake and the mixture intake (carburet¬
tor & manifold).

The thermostat air cleaner (TAC) is
the active portion of the air intake sub¬
system. The TAC has two functions: to
help maintain a carburettor temperature
of about 93°C, which is the design cen¬
tre, and to heat the air-fuel (AF) mix¬
ture, to aid in combining and atomising.
Some systems also use heating elements
placed under the carburettor.

Fig.l shows a vacuum (vac) type of
TAC. Some models have a thermostat
hooked directly to the damper assembly
door and do not require a vacuum
motor. Later models have a duct system

bringing in outside air, attached to the
snorkel. If the duct is removed, the sys¬
tem gets too much heat from under the
bonnet. People who don’t understand
the purpose of this system often disable
it, most often by blocking off vacuum.

TAC operation

In an engine’s initially cold state, the
TAC door is closed to hot air. When the
engine is started, the vacuum, via the
thermostat (or sensor) vac switch, oper¬
ates the vac motor to open the door. This
allows hot air to enter from the exhaust
oven, which heats the incoming air and
this in turn heats the carburettor.

When the thermostat closes (at correct
heat), vacuum is switched off to the vac
motor and the door closes, allowing in¬

coming air only. On a hot start, the vac¬
uum is not available to the vac motor —
so the hot air door remains closed. This
is the default for a failed system; i.e.,
when there is no vacuum, the door re¬
mains closed.

Mixture intake

The mixture intake consists of a car¬
burettor (Fig. 2) and an assembly of pas¬
sageways called the intake manifold.
The carburettor mixes the air/fuel and
the intake manifold routes the mixture
to the valve intake ports, in a manner
which ensures that they all get equal
mixture volume and pressure.

The proportions of air and fuel in the
mixture delivered to the cylinder are
controlled by the carburettor. The pro-

REGULATING MODE
DIAPHRAGM SPRING

SNORKEL

INLET

AIR BLEED VALVE
PARTIALLY OPEN

DAMPER ASSEMBLY

VACUUM HOSES
w DIAPHRAGM

1TC- HOTAIR DUCT
DOOR

THERMAL AIR CLEANER ASSEMBLY

Fig.2 (above): The construction of a conventional curcurettor,
used to mix air and fuel in the correct proportions.

Fig.l (left): The components making up a vacuum-operated
thermostatic air cleaner (TAC).

ELECTRONICS Australia, October 1992

ELECTRIC

COOLING

Fig.4 (above): The construction of a typical thermostat.
Fig.3 (left): The components of an engine cooling system.

portions are expressed by the ratio of
the mass (weight) of air to mass
(weight) of fuel. This ratio is appropri¬
ately called the air/fuel ratio (AFR). In
normal operation, the AFR varies in the
range between 12:1 and 17:1.

The control over AFR is achieved by
the throttle plate, part of the carburettor
itself. The throttle plate, which acts as
an air flow valve, is controlled in turn
by your foot, moving the accelerator
pedal up and down.

Reviewing what we’ve said so far, the
TAC controls the temperature of the in¬
coming air, bringing it to a specified de¬
sign centre value. A disabled TAC
system greatly effects engine efficiency.
The mixture intake supplies fuel and air,
in a particular ratio (AFR), to the intake

valve ports,via the intake manifold. The
incoming amount is controlled (de¬
manded) by the throttle plate — i.e., the
accelerator.

If you find the AFR a little confusing,
think of it as showing X parts of air to
one part of fuel, and remember that
there is always much more air than fuel.

The cooling system

Is heat a friend or a foe? We most
often think of heat as a foe, since it usu¬
ally represents lost energy. It can also be
destructive, if not controlled properly.
But if it is controlled properly, it be¬
comes friendly and can be used to en¬
sure optimum engine operation.

The main purpose of the cooling sys¬
tem (Fig.3) is to maintain the engine

temperature at a prescribed optimum
‘design centre’ value.

Before we get into this, though, let’s
purge our minds of dis-information and
‘witches tales’.

‘We don’t need thermostats here!’
This is false — there are only two ele¬
ments that control engine temperature:
the fan and the thermostat. Without a
thermostat, most engines run too cold.

‘Water works fine, you don’t need
coolant’ This is false too — since Du¬
Pont developed anti-freeze, commonly
known as ‘coolant’ fluid, no engine has
been designed for water only, except
marine engines.

I find it easy to convey the importance
of temperature to electronics people. We
understand the idea of parameters hav¬
ing an optimum or ‘design centre
value’, because we have had to live with
this concept in electronics. So although
high temperature is most often the ‘foe’,
all this really means is that in practice
temperature must be controlled — just
as in electronics.

As you can see from Fig.3, the basic
components of the typical cooling sys¬
tem are the fan and the thermostat. The
fan is controlled by a thermal switch, or
may be switched on with the air condi¬
tioner. The thermal switch has a speci¬
fied temperature setting. In electronic
models, it may be computer controlled.
If your vehicle has a belt-driven fan,
make sure the belt is in good repair. A
slipping belt will cause overheating.

The thermostat (Fig.4) is selected to
regulate engine temperature to its de¬
sign centre value. It has a temperature
element (spring) that maintains a closed
position until the correct temperature is

Fig.5: The emission control system for a modern car , excluding the electronics.

ELECTRONICS Australia, October 1992

AUTO ELECTRONICS

reached, and then opens to cover an
opening. This restricts flow, causing the
coolant to rise in temperature. On most
modern cars the thermostat controls
temperature at just below the boiling
point of water (100°C).

Whenever you need to change a ther¬
mostat, make sure it is made for the
right temperature setting. On an engine
with electronic control, a 10° difference
may effect operation. The industry has
just started stamping the temperature on
the thermostat — it’s that important

Coolant

The amount (percent) of coolant fluid,
relative to the water in a new car used to
depend on whether it had an air condi¬
tioner fitted (any way to save a dollar!).
The effect of the fluid is to raise the
water’s boiling point, to a degree de¬
pending upon the percentage (or ratio)
of fluid to water. This information is
listed on the container. Some coolants
also have additives, to maintain a clean
cooling system. The containers all have
warnings against ingesting...

If you break down in the ‘bush’ and
plan on drinking the water-coolant mix¬
ture, don’t. If there’s nothing else, dig a
hole and use a piece of plastic sheet and
a tin to make a simple distilling system,
to extract the water and leave the rest
Otherwise you may need a rather larger
hole — for you!

Without coolant fluid added to the
water, the modern car engine would
most likely be boiling all the time. De¬
spite the common misconception of
coolant as ‘anti-freeze’, it’s actually
more important in summer than in win¬
ter. The only reason it is used in winter
is to stop expansion caused by freezing

VACUUM SIDE

IDLE WIDE OPEN

POSITION POSITION

VAPOUR SIDE

Fig.6: The positive crankcase

ventilation valve , or ‘PCV’.

— which may crack the engine block.
There are hand-held testers which indi¬
cate when coolant should be added or
changed.

The radiator cap is a deceptively sim¬
ple device which can allow an engine
system to self destruct. Its function is
very simple, but often misunderstood. It
is not just to allow for fluid expansion,
but to maintain pressure. Maintaining
pressure aids circulation and insures
that there is no air pockets in the system.
Some engines require pressure, because
the heads and even the water pump are
above the radiator.

This brings up another point: if you
are changing your coolant, read the
owner’s manual. Many a Jaguar and Re¬
nault owner has found out why — with
a very large bill, for another engine.

Radiator caps are rated by pounds of
pressure, and are so labelled. A tester is
available; see your local mechanic. If
you put the wrong one on, you’re in
trouble. A cap designed for too high a
pressure may cause hose or radiator
bursting; one for too low a pressure can
allow overflow and overheating.

Be very careful when working on a
hot coolant system. I know very few
mechanics who have not been burnt.
Bums are very, very painful, as I can
testify myself...

If you need to replace a coolant hose,
go for quality. Some cheap hoses will
cut when tightening, and have a ten¬
dency to collapse. Hoses and belts
should be changed periodically — see
your local mechanic. Don’t be that
bloke broken down with a steaming en¬
gine, in the middle of Pacific Highway
in peak hour traffic.

E & P controls

Many people think that emission and
pollution controls are only on electroni¬
cally controlled vehicles, but this is not
true. What happened is that as pollution
standards rose, the mechanical, electric
or vacuum operated systems could not
meet those higher standards.

Fig.5 shows an emission control sys¬
tem without electronics. As you can see,
it is quite complicated. For this article
we will concede that the optimum AFR
of 14.7:1 could not be achieved without
electronics, and discuss only engine
emissions.

Engine emission control regulates en¬
gine and fuel tank vapours. The engine
vapours are controlled by a PCV (posi¬
tive crankcase ventilation) valve, a very
simple device illustrated in Fig.6.

The PCV valve is placed where it has
access to the engine crankcase vapours
— usually in the engine valve cover. At
idle, the vacuum pulls the check valve
up, closing the vent. At cruise, the vac¬
uum drops, the valve drops, allowing
the vacuum to draw the vapours into the
intake manifold. If it fails in the up
(closed) position, the vapours may be
seen escaping from the oil filler tube; if
it sticks down (open), you will have a
vacuum leak. This will cause hard starts,
stalls and poor or no idle, with very little
effect at cruise.

To control fuel tank vapour emissions,
a vapour collection tube runs from the
fuel tank to a charcoal canister, under
the bonnet. Vacuum pulls the vapour to
the canister, where it is stored. At cruise,
vacuum from the intake manifold draws
the vapours into the manifold. Note that
this is basically what happens; exactly
how it is done depends upon the system.

Electrical system

As we all know, the modem car de¬
mands a lot of electrical power. Some
luxury cars have alternators that will
supply 2kW, and starter motors that
draw up to 450 amps. The high currents
demand good cables and connections.

Fig.7: The modern alternator contains a three-phase AC generator with a
matching rectifier system, and uses electronic voltage regulation .

ELECTRONICS Australia, October 1992

Fig.8: The starter motor. It may need to draw up to 450amps to crank a large, cold
high compression engine.

Modem alternators have very good
reliability and require very little mainte¬
nance. Checking the driving belt and the
connections is all that is required. Most
failures are traced to an over-current
condition — i.e., a bad or shorted load,
generally a bad battery.

Most of you probably know how al¬
ternator works, so it will not be dis¬
cussed in depth. As Fig.7 shows, it is an
AC generator with built-in rectifier di¬
odes and a regulator (internal or exter¬
nal) that controls the output by
controlling the DC field current. The ad¬
vantages over the DC generator for¬
merly used are that output is controlled
by demand, and is more easily con¬
trolled. Some alternators also output AC
voltages for external use. Of course the
main function of the alternator is to
maintain a fully charged battery.

The starter motor

This was Dr Kettering’s first inven¬
tion, back in 1912 (Fig.8). The high
compression engine has placed an in¬
creased demand on starters; with a large
engine starting cold, up to 450 amps
may be required. The manufacturer is
faced with increasing the current capac¬
ity or using reduction gears.

The starter is a DC motor with high

current requirements. Most fail because
of low supply voltage — generally
caused by poor cables, poor connections
or a sick battery.

A surprising number of auto problems
are caused by poor earth paths — which
can produce anything from failure to
start, to instrument panel fires.

I personally test earth connections
with power on, using a voltmeter to
check for any significant voltage drop.
If there is any, the connection is bad...

Laymen should beware when
‘tapping’ their car’s electrical system to
run accessories. A lad I know powered

his stereo booster amplifiers off the cir¬
cuit that powered the car’s computer.
When he turned the boosters on, the
fuse to the computer blew. A word to the
wise...

Next time, we’re going to take a look
at maintenance. To keep an automobile
in operating condition is just as import¬
ant as in electronics, and involves
scheduled routine maintenance and
timely visual inspections. Weekly or
monthly visual inspections are a must,
and when a problem is found, fix it —
now. It won’t get better later, just cost
more! ♦

FORUM

(Continued from page 43)
quency and phase response desired—as
the R, L and C of a cable are directly
related to the material and size of the
conductors, their separation and the di¬
electric used. Not only would this tech¬
nique lead to less guesswork about what
cable may be best; it would probably
lead to a much lower-cost solution.

Well, there you are. My thanks to
Brendan Jones for sending in a copy of
his report, and allowing me to reproduce
from it. In some- areas, I guess it either
repeats some of the points that have been
made by either other readers or myself in
previous discussions, but by expressing
them in a different way Mr Jones has
contributed further clarification.

I don’t know about you, but I was very
interested to see the results of the mea¬
surements that Mr Jones was able to
carry out, some of them using using quite
esoteric and expensive equipment that
few of us have access to. It’s gratifying
that his measurements basically backed
up what my own intuition and experi¬
ence have caused me to say all along:
that the only objectively demonstrable
‘critical parameters’ of a speaker cable

are that it should have a low resistance,
and a reasonably high current-carrying
capacity.

What did you think about Mr Jones’
suggestion that it may be the slight in¬
crease in volume provided by some of
the really ‘huge’ speaker cables, by vir¬
tue of their slightly lower resistance, that
causes people to judge them as ‘better’?
Perhaps he’s right — it’s probably as
likely an explanation as many I’ve heard,
and it may explain why I myself simply
couldn’t hear what / regarded as any sig¬
nificant difference, when I compared the
very expensive Cardas cables with ca¬
bles consisting of ‘doubled-up’ heavy
mains flex.

Mr Jones’ suggestion of a possible fol¬
low-up experiment is also an interesting
one. If the ‘sound’ of one of those really
expensive cables could be simulated
using a low-cost lumped parameter filter,
even the platinum-eared brigade could
save themselves quite a lot of brass — or
even gold-plated, oxygen-free, single
crystal copper!

And that’s about all we have space for,
this month. I hope you’ll join me again
next time, when we’ll look at some other
areas of interest and controversy.

I think we’ll give fancy audio cables a
rest for a while though, don’t you? ♦>

- \

NEW KITS FOR
EA PROJECTS

The following new kits have been
released for recent EA projects:

LOW COST AUDIO SWEEPER
(August-September 1992): Dick Smith
Electronics has released a kit for this
project. The kit includes all specified
components, and features a pre¬
punched and silk screened front panel,
a pre-punched rear panel with descrip¬
tive label, and a 12V plug pack. Also
included are all of the electronic com¬
ponents for the measuring microphone
— everything except the metal tubing.
The DSE kit is listed by Cat. No. K-
7352 and is priced at $109.00.

FLEXIBLE SPEAKER PROTEC¬
TOR (October 1992): Jaycar
Electronics is releasing a kit for this
project. The kit includes the PCB and
all components except those for the op¬
tional power supplies, and features 1%
resistors, MKT metallised polyester
capacitors and a heavy duty relay with
10A contact rating. The Jaycar kit is
listed by Cat. No. KA1745, and is
priced at $29.95.

NOTE: This information is published
in good faith , from information supplied
by the firm or firms concerned and as a
service to readers. Electronics Australia
cannot accept responsibility for errors
or omissions.

ELECTRONICS Australia, October 1992

JET EXPRESS DELIVERY* AUSTRALIA U "0E

Phone Your Order To Us Toll Free

We guarantee our Jetservice Courier will deliver
to your door faster than any other Australian
supplier (including that local supplier just up the
road). If we fail, I’ll give you your money back
plus $5.00 for your inconvenience.

240V PowerRelay
Kit

(EA Jan ’92)

Here's a
simple
project that
monitors the power
drawn from a
‘master’ socket
and automatically
switches on a ‘slave’ socket. It will
monitor one or several appliances
plugged into the ‘master’ and switch on
one or several devices plugged into the
‘slave’. Ideal for Hi-Fi’s or computers with
peripheral hardware.

K 6070 $59 .95

Solar Generator Kit

(ETI Dec ’87)

Charge Your
Batteries Free From
The Sun. The Solar
Generator charges
and maintains your
standard 12V lead
acid car battery via
the sun. Ideal for
boats, caravans

and remote data acquisition stations etc.
Must be used in conjunction with a
suitable solar panel.

K 1680

2 Sector Alarm
System Kit

(EA March/April ’89)

Features: • Includes
12V 1.2 Amp hour
inbuilt sealed lead-
acid backup battery •

Easy to build,
assembles on a single
PCB • Two sectors -
delayed and instant
inputs • Entry and exit
delay • Panic alarm
input • Line
monitoring • Soft pre¬
alarm • Lamp tell-tale
output • Auxiliary
relay for external siren
etc • Key switch operation • Operates on
virtually any type of sensor

Four Digit Combination
Lock Kit tAA

(SC Dec 90) K1.2S $44.50

This 4 Digit Combination Lock is bound to prove
useful in many applications. Such as accessing alarm
systems, electronic doors, ignition killers or just
about anything that comes to mind. Momentry or
latched relay output.

K 1910

$89

.00

$13.i

! sar

Baby Room Monitor
& FM Transmitter
Kit

(SC Jan ’91)

This Baby Room ^MONiroH

Monitor allows

you to listen 0

to your baby

from a remote

location using a conventional FM
receiver. It runs from a single 1.5V AA
battery and includes a muting facility so
that it only transmits sounds above a
certain level.

K 1180 ifr^.95

4 Channel Guitar
^Mixer & Preamp Kit

(SC Jan 1992)

This
project
takes
advantage
of the
new low
noise,
low cost
op amps
available.

This unit

features separate bass, midrange and
trebel controls, very low noise and
distortion, separate input level controls
plus an output level control. Ideal for use
with most musical instruments from
keyboards to guitars to tape decks. In
fact, you can feed it with just about any
audio signal — it’s not just limited to
guitar outputs.

New 4-Channel Lighting Desk

(SC June/July ’91)

Make your stage production a professional
show with this new Lighting Mixer. Ideal for
amateur theatre groups bands etc.

This 4-channel lighting desk is intended for
theatre, disco and music group applications.

It has heavy duty circuitry and is able to cope
with spotlights rated up to 1000 watts or
more. It has been designed and built for the
rigours of commercial use. You can flash
each channel up to any brightness as set by
the 'Flash Master' fader. Similarly, the
'Channel Master' control fades all lights up or

■ ■ HHHII

Ni-cad Battery
Discharger Kit

Designed to rid your ni-cad
batteries of the memory effect’
and regain full re-charge
potential. It discharges your ni-
cad batteries correctly to enable
a full and proper re-charge. Suit!
most battery packs. Great for
mobile phones, rechargeable
drills, remote controlled toys etc.

K 5535

$49

.95

K 1640

$24

Transistor Teste
Kit

(EA Aug ‘83)

Checks transistor in
circuit. "No need to
unsolder suspect
transistors”. Have you ever
de-soldered a suspect
transistor, only to find that J
it checks out OK?

Features: • Tests both
NPN and PNP transistors _

in circuit at the touch of a switch • Tests
Diodes and SCRs as well • No need to
switch between NPN and PNP — it's
automatic • LED indication to show
condition of device.

down, to or from their individual fade settings. Two chaser faders control the rate
and lamp brilliance when the unit is operated in chaser mode. The lights can be
flashed to full brilliance or to an intermediate setting as set by the 'Chaser Master’

K 5815 Normally $3^0^00 This Month $299 •00_

Mini Home PABX Telephone Exchange Kit

(SC Aug/Sept ’92)

This great unit allows you
to place calls on hold,
intercom other extensions,
answer calls from any
extension and transfer
calls. It is expandable up
to 10 extensions, and is
compatible with all DTMF
(touch tone) telephones.

Operation is as simple as
pressing to place a
call on hold, press the 1

extension number (0-9)

and the respective station rings. Once answered, you have a two way intercom,
with which you can announce a call. To pick up the incoming call from hold
press A neat feature is that all extensions will ring when an incoming call is
placed on hold for 30 seconds so that it won't be forgotten. Basic kit is
complete with power supply, case and facilities for 3 extensions Extra
extension boards allow expansion in multiples of 3. Simple operation, fantastic
for home or small office. No more shouting from room to room. A T .

(MOA NB: Not Telecom

K 1430 Basic Kit $ I 89.00 K 1435 Expansion Board $79.95 Approved

Dec ’89)

Digital Voice Recorder Kit <sc

This Digital Recorder delivers astonishing
reproduction of voice and/or music without
any moving parts. It can store 4 different 30
second messages or 1 recording up to 2
minutes. Typical applications include • Alarm I
system messages • Sales messages for
customers put on ’hold’ • Talking Displays
for shops • Emergency warning messages •

And countless other applications where voice or music is required • K 9550 PCB alor
version • K 9555 Includes fully punched & screen printed instrument case.

K 2530

$17 50

K 9550 PCB Format $129 .95

K 9555 With Instrument

Case $149 95

Adjustable 0-45V, 8 Amp Bench Power

Supply ( sc Jan/Feb 92, R 3360 $375 ,

Using state of the art
circuitry this supply will be a
great asset to the enthusiast
and professional alike. It
uses switch mode principles
which allows for smaller
transformers, and
heatsinking which means
greater efficiency, less heat
and lighter weight.

Features: • Variable output • Variable current limit • Separate Earth Terminal •
Individual Volt and Amp Meters • Constant 13.8V setting • Short circuit proof
Specifications: • Output voltage 0-45V • Output current 8A @ 35V, 6A @ 40V •
Load regulation 1% • Ripple and Noise 40mVp-p at 8A 35V • Current limit 800mA-
8.6A • Over current limit 9A • Foldback current less than 2A

Laboratory Power Supply Kit

(EA May ’85)

K3300 $195 oo

3-50 Volts at up to 5 Amps

This supply has been one of
our most popular. It
includes the latest
refinements and is now
housed in a tough ’ABS’
instrument case. This
compact version uses a
high efficiency toroidal transformer resulting in less heat and weight.

• Exclusive to Altronlcs • Deluxe instrument case • Attractive silk screened front
panel • Pre-drilled and punched chassis — No holes to drill • Front panel drilled
for K 3302 option.

Specifications: • Output Voltage: 3 to 50V • Output Current: 5 Amps Max

• Floating Output • Ripple: less than 5mV • Dual Meters

10 Turn Pot For Precision Voltage Control Option K 3301 $4.50
Fixed +/-12V Rails Independant of Main Output K 3302 $14.50

PHONE ORDER TOLL FREE 008999007

JET EXPRESS DELIVERY- AUSTRALIA WIDE

Famous Altronics Inverters

Get 240V AC from your car, truck or boat battery. The Altronics range
includes an inverter for nearly every application. Fantastic for camping,
boating, farms and anywhere else 240V AC isn’t available. Each size inverter
is available in kit form or fully built and tested. The 300 and 600 Watt
Inverters now feature new improved circuitry using multiple mosfet outputs
making them even more reliable with a genuine 300 or 600 watt continuous
power rating. Our latest model, the 1200 Watt Powerhouse offers excellent
value for money and performance. It features crystal locked circuitry and a
massive 2400 watt power surge making it ideal for small fridges, vacuum
cleaners, power tools etc.

Any model an absolute necessity where 240V isn't available. Call Altronics
today for more information on freecall 008 988 007

300 Watt

K 6750 Kit Version $279
K 6755 Built-up $379

Vifa Speaker Kits

These kits use quality Vifa speakers made in
Denmark and specially engineered enclosures for
optimal performance. Black wood grain veneer
make them ideal for any deccr and situation. These
two way models include high grade crossovers,
speaker terminals and removable front grille.

Simply construction with only basic tools and skill
required. These kits are complete and include
speaker cloth, damping material, grille cups,
speaker terminals, screws and parts. Outstanding
performance for the fraction of the cost of
commercial equivalents.

VIFA SA-50

2 Way Bookshelf
System,

50 Watts RMS

Normally $390^00 pr

Now Only $299.00 pr

'*«*»*,

600 Watt +

K 6770 Kit Version $499
K 6774 Built-up 12V Input
K 6775 Built-up 24V Input $02D

1200 Watt *

K 6790 Kit Version $799

K 6792 Built-up 12V Input
K 6793 Built-up 24V Input

BBSS**-’

300 Watt Economy
Inverter

Turn 12V DC to 240V AC. This
fantastic inverter will power lights, TV’s 1
tools, electric shavers and a whole host |
of other appliances. Great for camping,
out in the bush and any place where
240V is not available. Features: •
Complete with over current circuit
breaker • Fused 240V output • Built in
panel meter to monitor output voltage
• panel meter to monitor output
voltage • Strong steel case and
chassis.

VIFA SA-100

2 Way,

100 Watts RMS

Normally $7§a , So

Now Only $699.00 pr

Stereo Extension Ceiling
Speaker Kit

Want a set of high grade extension speakers for
the back patio, games room, den, workshop,
kitchen? Well here at Altronics we have put
together this great kit which includes speakers,
grilles, cable, screws and even a wall mounted
volume controller. The speakers are our high
quality 4” C 0626 dual cone drivers, with stylish
white grilles - ideal for mounting in the ceiling.
Volume control mounts in standard electrical wall
box and includes 6 volume settings as well as off.
Includes 2 x 20m cable.

C 0988 Normally $9^f)0, Now Only $69.00

M 8120 1

Weather Proof Monitor and Sound Column
Speakers

This fantastic new range of monitors and columns just have to be heard to be believed.
Designed by the Altronics engineer team with extensive consultation from audiophiles and
architects, these speakers are absolutely ideal for hi-fi extensions and P.A. Constructed
from rugged extruded aluminium and UV resistant plastic makes these units both
weatherproof and built to last. The drivers used are 4” carbon fibre with an inbuilt coxial
tweeter. Ported design makes bass response incredibly smooth and deep.

Two sizes available, 30 and 60 watts RMS. in a black or white powder coat finish. Mounting
these speakers are made’easy by employing the new ’’Wacki" bracket system. Call
Altronics today for a free colour brochure.

30 Watt Monitor Series

C 0924 8 Ohm White
C 0925 8 Ohm Black
C 0927 100 Volt Line
C 0928 100 Volt Line Black

$149.00 ea

^ hite $ 160 oo~

60 Watt Column Series

C 0936 100 Volt Line White &o>l C
C 0937 100 Volt Line Black ^^**9.00 ea

Audio Frequency Generator

Specifications:
Frequency:

-20dB, -40dB and fine adjust
Q 1540 Normally $ 3^6 .00 Now $250 .00

RF Signal Generator

With provision for internal
and external modulation
Specifications: Frequency
Range: 100kHz - 150MHz
in 6 ranges RF Output
Level: lOOmV rms
Accuracy: -7-3%

Modulation: • Internal
(30% depth): 1kHz •

External: 50Hz-20kHz •

Crystal Locked Oscillator

Q 1550 Normally 00 Now $225 .00

Famous
Vifa 5”

Woofer h s uge

We have a huge surplus of
Vifa C13WG-08-08 woofers. 1
These quality drivers offer
high performance in both
ported and sealed
enclosures. Exceptionally smooth respond
useable up to 5kHz. Careful design and
construction using rubber surround makes
it possible to obtain an amazing 50 watts
RMS power calabicity. Fantastic
replacement or new construction speaker.

C 3110 Normally $901)0 Now $49 .00

6.5” Carbon Fibre
Woofer

A fine driver using only high
quality components and
technology. For example
barium ferrite magnets,
revolutionary Kapton voice coill
and unique carbon fibre cones. ’

Because of the high water
resistant structure of carbon
fibre these speakers are ideal for boats and
automotive use. Max input power 70 watts
or 30 watts RMS. Resonant frequency
65Hz. See Altronics ’92 catalogue for full
details.

C 3034 Normally $8£<sf

This Month Only $59 .95

15” PECC Woofer

These Poly Emulsion Coatee
Cone (PECC) woofers offer
excellent quality and
performance. With a
maximum power rating of
200 watts or 120 watts
continuous and a frequency
response down to 30Hz
these drivers make an ideal
sub-woofer or replacement
bass speaker. Massive 2.5kg
nett weight. See Altronics ’92 _

catalogue for full details.

C 3032 Normally QZSS'OO ^ Q ^

This Month $169 .00 •«

Motorola Piezo
Tweeter

This new bullet
tweeter looks and
sounds great.

Genuine Motorola
KSN 1165A. Features
400 watt maximum
power capability
frequency response 1.8kHz to 30kHz and
SPL at 93dB (2.83v/1m). 91 x 91mm
mounting hole centres Specifications
available on request. Simply wires in
parallel to your woofer. No crossover or
capacitor required As it presents almost
no load to your amp it doesn’t effect the
overall speaker system's impedance.
Fantastic for hi-fi or disco speakers.

C 6160

$39

.95

Universal Wacki
Bracket

P' oU ^usU » li8
tn ^

Yet another Altronics innovation, proudly
designed and made in Australia. These
great new speaker mount brackets simply
screw onto the wall and speaker allowing a
universal 50° angle of adjustment. Suitable
for speakers up to 5kg. No special tools
required Available in white or black. A
must for any extension speaker
H 8010 White ^

H 8012 Black $39.95 pair

PHONE ORDER TOLL FREE 008999

JET EXPRESS DELIVERY- AUSTRALIA WIDE

Universal Battery Chargers

As a result of a bulk scoop purchase, we
are able to offer to you these fantastic
universal Ni-Cad battery chargers at a
more than ridiculous price! It will charge
any combination of up to 4 of AAA, AA, C
or D size batteries at one time plus a 9V.
Features a LED indication to show each
battery has made an electrical contact.

Also has an added bonus of a battery tester
function. Hurry. Stocks limited. Definately
no back orders.

M 8010

Normally $3jHs This Month Only $19.95

LID NOT SHOWN

Performance Computer Fans

High quality computer fans ideal for power
supplies, amplifiers, computers etc. Reliable
Sunnon brand. Full range available for almost any
application.

240V Models

F 1020 80 mm 2 $22 .25
F 1030 120mm 2 $24 .25
12V DC Model
F 1050 80mm 2 $17 .50

24V DC Model
F 1040 120mm 2 $23 .90

Finger Guards

F 1022 80mm
F 1032 120mm

$2.45

Passive Infra-Red
Flood Light Control

S 5350

Sturdy Spotlight
Relay

Just arrived, this new model PIR floodlight j
activates when it detects movement of a
person or car approaching. Great to
welcome visitors, ward off intruders
or even to find the keys in the dark! Features '
daylight sensing circuit which means unit will
not activate during daylight hours (save on your
power bill). Includes manual override facility to
turn lights on continuously or automatically. Features
movement sensitivity adjustment, and turn on period. Great for the driveway or backyard.
Complete with two screw in type sockets for standard 150W floodlight globes (not
included).

Amazing Value on Deleted UHF Alarm

This UHF system contains one receiver
and 3 wireless reed switches for doors
and windows etc. The main controller
simply plugs into 240V, the remote, reed
switches are attached to your
door/window frames and presto, the
alarm is installed! Simple push button
operation, 4 digit user selectable on/off
code, built-in siren makes this unit a
pleasure to use. Includes 12V 1.2Ah
backup battery and 9V batteries for

remote reed switches. Because there is Central Control Unit
no need to drill holes in the wall or
ceiling, making this unit just great for
rented flats or units, or for those who
don't want the trouble and hassle of a
wired system. Also ideal for boats,
caravans, the shed, garage or granny flat
Take the unit with you if you move - no
wasted time and money.

Includes two separate
30 Amp relays with
individual fuses. Great
for car headlights, spotlights e'Sc.

S 4335 Normally $1
This Month Only I

Chassis Mount
RCA

Sockets *8

3 rows of stereo (left and right)
sockets. High quality. Bargain price.

PA 0235 Normally
This Month Only $1 .50

Universal Re mote
Control

with Built-in Siren & Battery Backup
SB 5260 Normally $5J^00

Now only $249 .00

Wireless Door
Reed Switch

Remote Car Alarm

With Wireless Remote Control

Audible warning with a 125 decibel
loud siren and visible warning of
flashing headlights when the alarm
system is triggered. Keyring remote
control allows arming with 'beep'
sound and disarming with headlights
flashing signal The alarm system will
be triggered by unauthorised
entrance through the car doors,
boot, bonnet or removal of the car
sound unit. The siren will sound and
the headlights flash for 60 seconds.
Easy to Install. nn

S 5220 $99.00

This universal infra-red
remote control makes all
other remote units
superfluous. Will control
CD players, videos, TV’s
and stereos etc. Controls
up to 6 different
appliances. Easy to use
and programme from an
existing functional remote !

A 1000

$69

12 Way Wire-
Product Terminal
Blocks

•tf* ,'jrt &■ f* 1 ,<*”i «• • r *’ •*' «

..1;! M X ,'iMl JV MW ,'t

i W i

These terminal blocks are ideal for
240V, speaker or DC voltage
termination. Can be cut into shorter
strips Raised base for extra voltage
protection.

PX 2110 Normally

Now Only $3.50 or 10 up $3 .00

Stationmaster
CB Base
Antenna

Extra wide bandwidth base
antenna without ungainly size.
Supplied with a fully pre-tuned
and assembled DC grounded
matching system and all
mounting hardware.
Waterproofed and useable at
any height above the ground,
earthed or unearthed. • 50
Ohm impedance • V.S.W.R.
1.3:1 • Height 5.6m • Power
IkW

L 3215 Normally

This Month Only ! $99.oo

Blank Rack
Panels

_ i liiBBMMBMIlllllIBB— II 111 Mill 1 IllllWIli IIHH

Top quality blank panel clearout. All stock must go at

these crazy prices. Stock is limited with definately no back orders at

these prices.

2 unit — All $8.00 3 Unit — Ail $12.95

H 0422 Natural Aluminium H 0423 Natural Aluminium

H 0432 Grey H 0433 Grey

H 0435 Black

HEAVY HEAVY SERVICE — All orders of lOKgs or more must travel Express Road —
Please allow 7 days for delivery. $12.00 to lOKgs. $15.00 over lOKgs.

INSURANCE — As with virtually every other Australian supplier, we send goods at
consignees risk. Should you require comprehensive insurance cover against loss or
damage please add $1.00 per $100 of order value (minimum charge $1). When phone
ordering please request "Insurance".

TOLL FREE PHONE ORDER — Bankcard. Visa, Mastercard Holders can phone order toll
free up to 6pm Eastern Standard Time. Remember with our Overnight Jetservtce we deliver
next day.

ALTRONICS RESELLERS Chances are there is an Altronic Reseller right near
you — check this list or phone us for details of the nearest dealer
Blue Ribbon Dealers are highlighted with a ■ These dealers generally carry a
comprehensive range of Altronic products and kits or will order any required item for
you.

ALTROniO

174 Roe St. Perth W.A. 6000 Phone (09) 328 1599
PHONE TOLL FREE 008 999 007

MAIL ORDERS C/- P.O. Box 8350 Stirling Street PERTH W.A. 6849

STANDARD DELIVERY A PACKING CHARGE $3.50 to 500gms, $5.50 500gms - 1 Kg. $8
1 Kg-5Kg AUSTRALIA WIDE — We process your order the day received and despatch via.

Australia Post. Allow approx 9 days from day you post order to when you receive goods.

OVERNIGHT JETSERVICE Up to 3Kg is $10.00, 3Kg to 5Kg is $23.00 - We process your
order the day received and despatch via Overnight Jeteervlce Courier for delivery next day
Country areas please allow additional 24-48 hours

WA COUNTRY ALBANY BP Electronics ■ (098) 412681 Micro Electronics (098) 412077 BUNBURY Micro Electronics (097) 216222 ESPERANCE Esperance Communications (090)
713344 MANDURAH Lance Rock Retravision (09) 535 1246 PORT HEDLAND Ivan Tomek Electronics (091) 732531 ROCKINGHAM TV Joe s (09) 5271806 NT ALICE SPRINGS Farmer
Electronics (089) 522388 DARWIN Ventronics (089) 853 622 VIC All Electronic Components (03) 6623506, TECS (03) 6706474 BORONIA Ray Cross Electronics ■ (03) 7622422
CHELTENHAM Talking Electronics (03 ) 5842386 COLLINGWOOD Truscott Electronics (03) 4198208 CROYDON Truscott Electronics ■ (03) 7233860 FOOTSCRAY G.B Telespares
(03) 3179100 PRESTON Preston Electronics ■ (03) 4840191 COUNTRY BAIRNSDALE LH & LM Crawford (051) 525677 BALLARAT Ballarat Electronics (053) 311947 OLD Delsound
PL ■ (07) 8396155 WEST END B.A.S. Audiotronics (07) 8447566 WOODRIDGE David Hall Electronics ■ (07) 8082777 COUNTRY GLADSTONE Gladstone Electronic Services (079)
724459. Electronic Enterprises (079) 726660 MAROOCHYDORE MALS Electronics ■ (074) 436119 MARYBOROUGH Keller Electronics (071) 214559 NAMBOUR Nambour Electronics
!?I 4 L 411966 P,ALBA Kel,er Electronics (071) 283749 ROCKHAMPTON Access Electronics (East St.) (079) 221058 TOWNSVILLE Super Solex ■ (077) 724466 SA Force Electronics ■
(08) 2125505 BRIGHTON Force Electronics ■ (08) 3770512 CHRISTIES BEACH Force Electronics ■ (08) 3823366 FINDON Force Electronics ■ (08) 3471188 HOLDEN HILL Force
Electronics ■ (08) 2617088 LONSDALE Force Electronics ■ (08) 3260901 ENFIELD Aztronics ■ (08) 3496340 COUNTRY WHYALLA Eyre Electronics (086) 454764 TAS HOBART
George Harvey ■ Georfle Harvey ■ (003) 316533 NSW David Reid Electronics ■ (02) 2671385 REVESBY Revesby Electronics (02) 7922295 SMITHFIELD

Dirtribi^tonf HARBOUR Coffs Habour Electronics (066) 525684 NEWCASTLE Novocastrian Elect.Supplies (049) 621358 WARNERS BAY Vilec

Distributors (049) 489405 WINDSOR M & E Elect, and Communications (045) 775935 WOLLONGONG Newtek Electronics ■ (042) 271620, Vimcom Electronics (042) 284400 WOY WOY
Alphatran Electronics (043) 434919

PHONE ORDER TOLL FREE 008 999

Experimenting
with Electronics

by PETER MURTAGH

Electronic thermometer

Last month’s project, our LED ‘loudness display’, can be easily adapted to display changes in
temperature. How warm is your room, how hot is your bath water? Build this circuit, and you can
find out!

The five LEDs in last month’s project lit
up in turn as the sound picked up by the
microphone became louder — to turn on
each extra LED required a further 0.5V
increase in the output. This month we will
re-use the same LED display circuit, but to
sense the temperature differences we will
use a thermistor — a new component to
this series.

As with last month’s circuit, the signal
from the sensor needs to be amplified, but
this time we will use a DC amplifier in¬
stead of an AC one. You will find, if you
compare this and last month’s schematic
diagrams, that despite looking very much
the same on first inspection, the feedback
arrangement for the two amplifiers is real¬
ly quite different.

We have also made some minor changes
to the LED display section — diode D1 no
longer needs to feed into a capacitor to
smooth its rectified AC signal, and each of
the five LEDs now has its own current-
limiting resistor. While this latter
modification is not really necessary, it
does make the LEDs glow a little bit
brighter since they no longer have to share
a fixed current.

The use of a thermistor is interesting,
because normally we have to stabilise our
circuits to overcome current changes
caused by changing temperature — such

changes are usually regarded as a prob¬
lem. However, we have chosen a thermis¬
tor as the sensor for this project precisely
because it is sensitive to temperature chan¬
ges. A ‘thermistor’ is literally a tempera¬
ture-sensitive resistor (‘therme’ is the
Greek for heat).

Data for thermistors is quoted as their
resistance at 25°C. Quite often, some in¬
dication of how much they vary will
also be given. For example, the ther¬
mistor we used (DSE Cat. R-1797) is a
100k thermistor, with a -5.2% change per
degree Celsius. Recognise its colour
coding (reading from the leads)? —
brown-black-yellow.

The quoted percentage resistance varia¬
tion is only an approximation, since the
resistance change is not linear with
temperature. But we can work out that our
sensor will vary from about 230k-30k as
the temperature varies from 5°- 50°C.

Note that the resistance decreases as the
temperature increases , which is the op¬
posite to a normal ohmic resistor. Such a
thermistor is called an NTC thermistor
(Negative Temperature Coefficient), and
this explains the minus 5.2% change given
in the Dick Smith data. (Positive tempera¬
ture coefficient thermistors also exist.)

We have used this thermistor resistance
change to alter the voltage at the base of

transistor Ql, so that the amplifier built
around transistors Ql and Q2 will increase
its output as the temperature increases. We
have added trimpot RV1 so that you can
adjust the point at which the first LED
turns on (the start of your temperature
range), while trimpot RV2 allows you to
alter the gain of the amplifier (the total
temperature range covered from ‘no LEDs
on’ to ‘all LEDs on’).

By varying the two trimpots, we had no
trouble in calibrating our ‘thermometer’
for two different temperature ranges: 5°-
30°C (typical room temperatures), and
10°-50°C (typical tap water temperatures:
cold water in winter and ordinary domes¬
tic hot water).

Construction

If you have already built last month’s
‘loudness detector’ circuit, and wish to
convert it to measure temperature change,
you only have to add the DC amplifier
section — shown on this month’s
schematic diagram to the left of diode Dl.

You will also have to modify the
original circuit by cutting the tracks be¬
tween the collector of transistor Q2 and
Dl, and between capacitor C3 and Dl.
The output of your new amplifier will
then be fed into the top (positive end) of
diode Dl.

Right: If you can't see all the connections on this
breadboard layout for the circuit , refer to the schematic
diagram for more details.

ELECTRONICS Australia, October 1992 97

Experimenting

The changing resistance of thermistor T affects the bias on transistor Q1.
Trimpots RV1 and RV2 set the start and range of the temperature scale (arrows
show trimpot clockwise rotation).

If you are building the whole circuit
from scratch (which the component list
and the rest of this article will assume),
then start your construction.

Solder the components in the usual
order, with the more rugged components
first: resistors, diodes (including the
LEDs), transistors and finally the thermis¬
tor. Take the usual care with the polarised
components.

Refer to Fig.3 to identify which lead is
which for the LEDs, diodes and transis¬
tors. As in last month’s project, Q2 is the
only PNP (BC558) transistor — the rest
are NPNs (BC548). The thermistor is not
polarised, so its leads can be inserted
either way.

If you only intend to measure air
temperature, then you can solder the ther¬
mistor directly to the PCB. But you will
probably want to measure water tempera¬
ture as well, so you need to waterproof the
sensor. (When our thermistor accidentally
got wet, its resistance dropped from its
normal 100k to about lk — which turned
all five LEDs fully on. And it took a few
days to fully dry out and regain its correct
resistance. So take care!)

Very simple waterproofing can be done
by wrapping the thermistor in thin plastic
sandwich wrap. Make a funnel shape in
the wrap and insert the thermistor. Then
use an elastic band to tie in the top edges
of the plastic.

However, this approach didn’t prove to
be very satisfactory. It proved difficult to
completely seal the plastic, so the water
sometimes leaked in. Also, the plastic
layers made the sensor a lot slower to react
to temperature changes.

A better probe can be made by sealing
the thermistor into the plastic casing of an
old ball-point pen (as shown in the photo
of our PCB design).

This method is more sensitive, since
the head of the thermistor makes direct

contact with the water whose tempera¬
ture we want to measure, and the water
itself is kept well clear of the
thermistor’s base and leads where it can
interfere with its resistance.

Calibrating

Once you have completed your circuit,
you then have to adjust the temperature
range to suit your requirements. Use RV1
to set the start of your range, and RV2 to
set the extent of the range. Unfortunately,
the two settings interact, so you will need
to adjust each trimpot a few times after
altering the other one.

If you wish to calibrate your circuit
quite accurately, you will find that a
laboratory-type thermometer will come in
very handy. In the absence of a ther¬
mometer, you can use a cold water/ice
block mixture (keep adding ice until it no
longer melts) to give 0°C, while the
hottest water from a hot water tap is usual¬
ly about 50°C.

Start the calibrating process by setting
both trimpots to approximately mid posi¬
tions. Then insert your temperature probe
in the cold water (or cold air, if you have
not waterproofed your sensor).

Turn RV1 anticlockwise to gradually
turn off the LEDs, or clockwise to turn

them on. Set the first LED as desired for
the lower end of your temperature scale —
fully off, just starting to glow, or fully on.

Next use your hot water to turn the
LEDs on. If they turn on too quickly, then
the gain of the DC amplifier is too high.
Turn it down, by adjusting RV2 anticlock¬
wise. Of course, if the probe reaches its
top temperature and all the LEDs are not
yet on, make a clockwise adjustment to
increase the gain.

If you had to decrease the gain (by
increasing the resistance of RV2), then a
side effect of this adjustment is that you
have also decreased Ql’s base current.
You will find, when you re-check your
lower temperature limit, that you will
need to turn RV1 slightly clockwise to
compensate.

Similarly, increasing the gain increases
the brightness of LED1 at its starting point
— which is another way of saying that
your scale now starts at a lower tempera¬
ture than your requirement.

Hence, after adjusting either RV1 or
RV2, you will have to adjust the other
trimpot We used two cups for the cold and
hot water standards, side by side, and al¬
ternately dipped the probe into each. After
several ‘ups and downs’, we were able to
calibrate the scale as required.

Fig-1: The component layout on the printed circuit board. Note that Q2 is the only PNP transistor — the rest are NPNs.
Fig.2: The stripboard layout. Make certain that you break the copper tracks at all the ‘cut track’positions.

ELECTRONICS Australia, October 1992

The PCB pattern is shown actual size to allow experimenters, if they wish, to make
their own boards.

Changes

The values of the two trimpots and their
associated resistors (RV1+R2, RV2+R4)
have been chosen to allow the temperature
scale to vary from about zero to 60°. This
should allow sufficient variation for most
applications. However, you can further in¬
crease the temperature range by increasing
the value of R4 and/or decreasing R3
(decreasing the gain) — or vice versa.
However, if you reduce the value of R4,
remember that R4 can be the only resistor
which limits both the emitter current of Q1
and the base current of Q2. So don’t make
its value too small or your transistors
could bum out!

You can also further adjust the starting
temperature. If you have turned RV1
fully anticlockwise and LED1 is still too
bright (or too many LEDs are on), then
reduce the value of resistor R2. The
smaller the combined resistance of R2
+RV1, the smaller the voltage at the base
of transistor Ql.

Resistors R11-R15 determine the
brightness of the LEDs. Our 560 ohms

PARTS LIST

Miscellaneous

PCB 90x50mm, coded 92et10
9V battery
5 LEDs, any colour
hookup wire, solder, etc.

Resistors

All 1/4W, 5%

1 220k R1
1 5.6k R2
1 2.2k R3
1 Ik R4
1 560k R5
5 10k R6-R10

5 560 ohmR11-R15 _

1 20ktrimpot RV1 horiz. mount
1 lOktrimpot RV2 horiz. mount

Semiconductors

red-red-yellow

green-blue-red

red-red-red

brown-black-red

green-blue-yellow

brown-black-orange

green-blue-brown

1 100k NTC thermistor

5 1N4148 signal diodes D1-D5

6 BC548 NPN transistor Q1.Q3-Q7
1 BC558 PNP transistor Q2

value gives a current of about 13mA. If
you want them brighter (and are not
using a battery), then decrease the value
below 560, perhaps to 470 or even 390
ohms; and if you are using a battery, then
make it last longer by decreasing the
brightness, and increase the resistance to
1.2k, or even 1.5k.

How it works

As mentioned earlier, the resistance of
thermistor T decreases as the temperature
rises. Since the thermistor is connected be¬
tween the positive supply rail and the base
of transistor Ql, this decrease in resistance
results in a smaller potential drop across T.
Because of this, the voltage drop across
the base-emitter junction of Ql increases
— so its base current increases, causing its
collector current also to increase. This in
turn causes increases in transistor Q2’s
base and collector currents.

As a matter of fact, we have ‘padded’
the thermistor T with a 220k resistor Rl.
By connecting Rl in parallel with T, we
can make the resistance variation more
linear, but connecting Rl this way also
reduces the total change in resistance from
30k-330k to 27.5k-104.5k. This reduction
comes in handy, since it allows us to ex¬
tend our temperature scale up to 60° — its
effect is equivalent to reducing the gain of
the amplifier.

Notice the arrangement of the main load
resistance for transistor Q2 — series
resistors R3+R4+RV2. These resistors
form a potential divider, with a tap back
to the emitter of transistor Ql. This con¬
nection provides negative DC feedback,
because an increase in the voltage at the
join of resistors R3 and R4 results in a
decrease in the voltage applied across
Ql’s base- emitter, and hence a decrease
in the current to be amplified by Q1/Q2.
Check these calculations for yourself, as¬
suming that transistor Q2 is turned hard on
and the voltage at its collector is 9V: if
trimpot RV2 is turned fully clockwise.

components used in the circuit.

the voltage at the emitter of Ql will be
2.8V, and if fully anticlockwise, 7.5V. So
the first position gives minimum feed¬
back and greatest DC gain, while the
second gives the exact opposite. If the
gain is at its greatest, then it will take the
smallest temperature range to turn all five
LEDs on.

We have set up the circuit so that turning
RV2 clockwise increases the brightness of
the LEDs. Hence, if you want a larger
temperature scale, then decrease their
brightness to take longer for them all to
turn on; and vice versa.

We will only briefly describe the opera¬
tion of transistors Q3-Q7 which drive the
five LED display. (If you want more
detail, refer back to last month’s issue.)

As the collector voltage of transistor Q2
increases, that voltage is applied to the
bases of the five driver transistors along
the diode chain, D1-D5. Since the voltage
drop across each diode is about 0.6V, it
takes approximately an extra 0.6V to turn
each extra LED on. This voltage drop is
slightly larger than in last month’s circuit,
because the base currents in transistors
Q3-Q7 are larger (this was explained in
more detail last month).

In practice, our measurements showed
that if the collector voltage of Q2 was
<0.9V no LED was on, and if it was
>3.8V all five LEDs were on. But the
increase was not linear — there was a
0.45V difference between the first and
second LEDs, but 0.7V between the fourth
and fifth.

Transparencies

A high contrast, actual size transparency
(negative) for the PCB used in this circuit
is available for only $2. This will allow
you to etch your own printed circuit board.
This special price applies for transparen¬
cies for all projects in this series only.
Write to EA's reader services division.

Happy experimenting — and please
send us your comments on the circuits
we have published, as well as ideas for
future projects. *

ELECTRONICS Australia, October 1992

BLUE LEDS ar ® now available
A blue LEO housed in tampered Tl 3/4
water clear plastic package. For a
suitable mounting clip and ring
length 8.8 body dia 5.0 Lead pitch 2.54
Leads 0.5aq Short Lead denotes anode

1-9 10-99

I Z10152..$3.75 $3.50 3mm

Zi0153 $3.75 $3.50 5mm

—

I NEW CHEAPER SOLDER PRICES |
{ 25% MORE PRODUCT THAN OUR J
{ OPPOSITIONS FOR THE SAME
I PRICE [’66/46ReaTn"Cored*j

ABSOLUTE TOP \

OUAUTY |
ROD IRVING ELECTRONICS1

„ 25% MORE *

SOLDER ROLLS

T31000.

. .71 mm 250gm

$8.95

T31002_

. .71mm 500gm

$15.95

*T31010—,

. .91mm 250gm

$7.95

T31012..

. .91mm 500gm

$14.95

T31020.

...1.6mm 250gm

$7.50

T31022...—

...1.6mm 250gm

$13.95

T31030.

. .71mm 1 metre

$1.50

T31032.

. .91mm 1 metre

$1.50

T31034.......

..1.6mm 1 metre

$1.50

nj nir . TT . Ttm m miT . TT . TT . Tt m rr tt , tt . tt , t? mrr

MES BATTERY HOLDEI
FOR GLOBES

1-9 10+

H11689.$1.95 $1.60

LINT AND DUST REMOVER

Blow away the dust and grime out of
those hard to get at places like buttons
on your car phone, keyboards or clean
your camera^

JlL

Nil 036.$9.95

CAR CD PLAYER
& AM FM RADIO

High power FM/AM stereo PLL
synthesized LCD digital car radio with
built in compact disc player and anti-theft
holder.

(Those long drives through the country
will be even more enjoyable with the
BEST sound quality)
only

A20100.$495

UNBELIEVABLE

I (NEED AMP FOR THE ABOVE CD
PLAYER TO WORK WITH BACK
SPEAKERS)

1 2 X 50W AMPUF1ER TO SUIT FOR BACK
SPEAKERS CAT..Cl 0778

NORMALLY OUR PRICE
$019-— $79

PIEZO TRANDUCER
can be used as a Audio ,
Speaker

SI 5252..

1-9

..$2.50

10+

$2.00

DB9 + DB25

j 4|^CUT OUT PLATES

1-9 10+

PI 0908 .$1.95 $1.60

HIGH PERFORMANCE
STEREO SPEAKERS FOR
PORTABLE C.D PLAYERS,
WALKMANS OR COMPUTERS.
IDEAL WHEN USING CD ROMS
These have a built in amp or can
operate direct from your stereo
earphone outlet
TAKES 2 "C” CELLS

Cl0174.$39.95 per pair

WOW 80387DX
MATHS COPROCESSOR
SMARTENUP YOUR 386

only..

..$249

DO YOU NEED A UART
SCOOP PURCHASE
16C450 (82450)

Features of a UART include
programmable data
format;parity,framing,and overrun error
detection etc.

UNBELIEVABLE!!

U22185.$9.95

SUPA HIGH SPEED UART

TEXTOOL 1C SOCKETS
(ZERO INSERTION FORCE)
These ZIF socket are perfect for
inserting and removing EPROMS so
as not to damage the 1C pins.

\ \v

\\r m

7 1-9

10+

• 16 pin

PI 7016.

.. $16.95

$13.95

• 24 pin

PI 7024.

.. $19.95

$18.50

• 28 pin

PI 7028.

...$26.95

$24.95

• 40 pin

PI 7040.

..$34.95

$32.95

pTA SPEaTerST 400- only in slock)']

jLow dual cons wids range. 200mm [
1(8 inch). Ideal for public address,
{background music,etc. Tremendous{
I Value at these prices!

! 1-9 10+
[Cl2000^jBp*T.....$5.95 $5.50 l

I QUICK REFERENCE BOOKS

PC TOOLS 7.B21302 $19.95

NORTON UTILITIES 6.B21304 $19.95

EXCEL 4 for WINDOWS.B23004 $19.95

Dr DOS 6.B23002 $19.95

MS-DOS 5.B21267 $19.95

RELEASE 2.4 1.2.3.B21264 $19.95

WORDPERFECT 5.1.B21268 $19.95

L-SHAPED CORNER
BRACKETS

60 X 18mm
pack of 4

with punched holes for screws

H11860.$4.95

Saves trying to bend them.

LED BAR GRAPHS
BACK IN STOCK

An end stackable LE.D. bar a S.I.L pin
package. Suited for solid state meter
movements and level indicators.

(10 leds in a row)

1-9 10-99

Z10180.... $3.95 $3.50

DON'T PAY $4.95 AT OUR OPPOSITION

NEW COMPUTER LABELS
You asked for labels for your laser
now there in! yt, n t T *

11 j, I ii mu

Label size 25.4mm x 98mm
20 labels per sheet 50 sheets per
packet (on a A4 sheet)

C20106.$39.95

for 1000 labels

Label size 38.1mm x 98mm 14 labels
per sheet 50 sheets per packet ( on
a A4 sheet)

C20108.$39.95

for 700 labels

rLabel size 37mm x 105mm
16 labels per sheet 50 sheets per
packet (on a A4 sheet)

C20110. $37.95

for 800 labels

FOR THE COMPUTER
SERVICE MAN

THESE QUITE OFTEN BLOW UP IN VGA
COLOUR MONITORS
LM1203 VGA INPUT DRIVER
1-9 10+

U10440.$12.95 $11.95

UNIX HEAT SINK COMPOUND

Heatsink compound is applied to the
base and mounting studs of transistors
and diodes. It maintains a positive
heatsink seal thet improves heat transfer
from the device to the heatsink, thus
increasing overall efficiency

(SAVE $10 A TUBE THIS MONTH)
NORMALLY weight..150g

H11810. ...SUPA SPECIAL $19.95

WE CARRY A LARGE
RANGE OF ELECTRICAL
PRODUCTS

FLOURO BATTEN HOLDERS
HUGE RANGE

(al ^holders come with fluoro tubes) ^

1-4 5+

S18000....1 X 18W $19.95 $17.95 LPF
Si 8010—1 X 36W $22.95 $21.95 LPF
Si 8020...1 X 36W $22.95 $21.95 HPF
Si 8030...2 X 36W $37.95 $35.00 LPF
Si 8040—2 X 36W $37.95 $35.00 HPF
^-

36 WATT FLUORO TUBE

1-9. 10+...

$4.95 $4.50

(WE ARE CHEAPER THAN THE
HARDWARE STORES AND BIG
NAME STORES)

ELECTRICAL HOUSE
WIRING CABLE

per metre 1-9m 10-99m

W11580 ....$1.50 $1.20 Light 1mm
W11590... $1.90 $1.80 Power 2.5mm
per 100m drum

W11580. $79.00 Light 1 mm

Wll590. $119.00 Power 2.5mm

THESE ARE VERY HEAVY AND
SUGGEST YOU PICK
UP FROM ONE OF OUR
STORES

SUSPENDABLE MAIN
SWITCH SOCKET

( GREAT TO SEND POWER DOWN
FROM THE ROOF)

SORRY NO PICTURE THIS
MONTH

F10010..

.$39.95

FREE STANDING,

FOLD UP
MAGNIFIER

An economically priced " hands free
"magnifier, lets you take care of all jobs
ao often encountered In electronics
Tl 0020.$14.95

ADELAIDE

SPECIALS OPENING WEEK
57MM SPEAKERS (21/4”)
1-9 10+ 100+

$1.00 85c 75C
(Available all stores)

FERRIC CHLORIDE
25%more from RIE for the
same price as from our
opposition.

|0£E'SQ|

Hi 0810 250gm...T??!T:. $4.95

Hi 0812 500gm.$7.95

i BNC PLUGS AND SOCKET

j BNC MALE PLUG

1-9 10-99 100+

I Pi 0514 $2.50 $2.25 $1.50

| BNC PANEL SOCKET

1-9 10+ 100+

| Pi 0516 $Z50 $2.25 $1.50

BNC CRIMP PLUG

1-9 10-99 100+
Pi 0530 $3.95 $3.75 $3.00

j BNC SOLDERLESS TWIST ON PLUG
1-9 1 0-99 1 00+

| Pi 0531 $3.50 $3.25 $3.00

CANNON PLUGS"AND SOCKETS"!
CANON TYPE 3 PIN UNE MALE
1-0 10 + 100 +

Pi 0960 $4.95 $4.75 $ 4.50

CANON TYPE 3 PIN CHASSIS MALE I

1-9 10-99 100+ A9m\ I
Pi 0962 $3.50 $2.95 $2.50

CANNON TYPE 3 PIN UNE FEMALE
1-9 10-99 100+

Pi 0964 $3.95 $3.50 $2.90

CANNON TYPE 3 PIN CHASSIS FEMALE
1-9 1 0-99 1 00+

Pi 0966 $4.95 $4.50 $3.50

DISCOUNT COMPONENTS

IXENON/STROBE

Itubes

■ As used in projects or
|as replacement.

|S1 4050.$3.95

■cat no.

|W12614

IW12616

IW12620

JW12624

JW12625

IW12626

IW12634

IW12636

IW12640

■ W12650

IW12660

14 way
16way
20way
24way
25way
26way
34way
36way
40way
50way
60way

S/Mtr

$1.90

$2.20

$2.50

$2.90

$3.20

$3.60

$3.90

$4.90

$5.90

$6.90

10 TURN WIRE
WOUND
POTENTIOMETER
ISpectrol Model
■5341/4” shaft.

■ Equivalent (Bourns
I3540S Beckman 7256)

■ Dials to suit 16-1-11,

!l8-1-11, 21-1-11.

R14050 50R R14100 5K

Iri4055 100R R14110 10K

■ R14060 200R R14120 20K

■ R14070 500R Rl40a0 IK
R14090 2K

1-9 10+

$12.95 $10.90

IR14130 50K.$16.95

I R14140 100K..$15.95

©©©
0(D@
CD © ©
0 © @

[NUMERIC KEYPAD

I Unencoded keypad, 10
■digit keys plus two utility
■keys. Light grey in colour.
■OUTPUT ARRANGEMENT:
■Output Pin No. Symbol

|1.-.N.A.

I 2 .Shield plate

■3 ....Column 2

.4.-.Row 1

Is ....Column 3

■6 .-.Row 1

■7 .-.Column 1

■8.-.Row 2

9 .—.Row 3

10 ....N.A.

? Cat Cl9030

11-9 10+ 100+

; $2.95 $2.50 $1.95

CHROME LED
[BEZELS

9 mm hole, available
|3 colours

■S14030 Red.$1.20

IS14032 Green.$1.45

IS14034 Yellow....$1.45

GREY FLAT
RIBBON CABLE

DIE CAST BOXES

Diecast boxes are excellent
for RF sheildingand
strength.

Screws are provided with
each box.

H11451

100 x 50 x 25mm..$8.95

Hi 1452

110 x 60 x 30mm..$9.50

H11453

120 x 65 x 40mm..$10.50

H11461

120 x 94 x 53mm.$13.95

H11462

188 x 120 x 78mm....$15.95
H11464

188 x 188 x 64mm....$29.50

GENERAL
PURPOSE
TRANSISTORS

PN100: • NPN general
purpose medium power
amp and switch with
continuous collector
current up to 500mA.
PN200: a PNP general
purpose amp at collector
currents to 1 AMP.

Both are TO-82 plastic
package.

PN100 REPLACES:

PN2221, PN2222, PN2222A,
PN3585, PN3568, PN3569,
PN3643, PN5133, 2N2219A,
2N2222A, 2N3414, 2N3415,
2N3416, 2N3417, 2N3700,
2N3704, 2N3904, 2N4123,
2N4124, 2N4401, 2N5088,
2N5210.

PN200 REPLACES:

PN2907, PN2907A, PN3638,
PN3638A, PN3640, PN3644,
PN4121, PN4143, PN4248,
PN4249, PN4250, PN4355,
PN4916, PN4917, PN5910,
2N2905A, 2N3467, 2N3702,
2N3906, 2N4125, 2N4126,
2N4291, 2N4402, 2N4403,
2N5086, 2N5087, 2N5447.

PN100.T90001

PN200.T90002

1-9 10+ 100+

$0.20 $0.18 $0.15

SUPER BRIGHT
LEDS

• RED.Z10146

-GREEN.Z10147

•YELLOW..Z10148

1-9 10+

$1.00 $0.90

CARD EDGE
CONNECTORS
1" SPACING
P12060 10pin $3.95 $3.
P12062 20pin $4.25 $3.
P12064 26pin $4.50 $3.
P12066 34pin $4.95 $3.
Pi2068 40pln $5.95 $4.
P12070 50pin $6.95 $5.

DIODES

—

BUY IN BULK & SAVE!

Cat No.

10+

100+

1000+

10K

Z10135 IN4148

$0.05

$0.04

$0.03

$0.02

Z10105 IN4002

$0.06

$0.05

$0.04

$0.03

Z10107 IN4004

$0.08

$0.06

$0.05

$0.04

Z10110 IN4007

$0.10 :

$0.07

$0.06

$0.05

Z10115 IN5404

$0.18 $0.14

$0.13

$0.11

Z10119 IN5408

$0.20 $0.16

$0.15

$0.14

i in*

* X X * X

11A111

xTxx^xxl

POWER SUPPLIES

XT P.S 1$6W....$139.00

FULL TOWER

220W P.S.-...$149.00

MINI TOWER

200W P.S....$89.00

BABY AT

P.S 200W..$89.00

SLIMUNE BABY AT
P.S. 200W....$89.00

BREAD BOARDS

This inexpensive range of
modular interlocking units
enables a quick easy way
of experimenting with new
circluts and ideas. There
are two main units
consisting of a terminal
atrip or distribution and a
central plug in unit

• 100 holes.

Pi 1000.$2.75

•840 + 100 holes
P11007.$14.95

• 1280 +100 holes

•P11010.$26.95

•2560 + 700 holes

• P11018.$69.95

COMPUTER

CABLES

• Six conductor ahlaldod
computer Interface cable.

W12670 • CIC6 6 con.

1-0M 10M+ 100M+

$1.30M $1.10M $1.00M
W12672 • CIC9 9 con.

1-9 M 10M + 100M +
$1.60M $1.50M $1.20M
W12674 • CIC12 12 con.

1-9M 10M+ 100M+

$2.50M $2.20M $1.90M
W12676 • CIC16 16 con.

1-9M 10M+ 100M+

$3.50M $3.20M S2.50M
W12678 • CIC25 25 con.

1-9M 10M+ 100M+

$3.90M $3.40M $3.00M

iHsii

NICADS

Save a fortune on
expensive throw away
batteries with these
quality Nicads and
Rechargers!

Size AA 4 50mAH

1-9 10+ 100+

$2.95 $2.75 $2.50

Size C 1 2 A M
$9.95 $9.50 $8.95

Size D 1 2 A H
$9.95 $9.50 $8.95

LOW PROFILE
1C SOCKETS

Save a small fortune on
these "Direct Import" low
profile 1C sockets! PCB
mounting solder tall. All tin
plated phosphor bronze or
berrylllum and dual wipe for
reliability.

1-9 10+ 100*

Pi 0550 8 pin 15« 12c 10c
P10560 14pin 20c 18C 15c
P10565 1 6pin 20c 18c 16c
P10567 1 8pin 30c 25c 22c
P10568 20pin 35c 30c 25c
Pi0569 22pin 35c 30c 26c
P10570 24pin 35c 30c 26c
P10572 28pin 45c 35c 30c

WIRE WRAP
1C SOCKETS

These quality 3 level wire
wrap sockets are tin plated
phosphor bronze.
P10579 8pin $1.50 $1.40
Pi0580 14pin $1.85 $1.70
Pi0585 16pin $1.95 $1.80
P10587 18pin $1.95 $1.80
Pi0590 20pin $2.95 $2.75
P10592 22pin $2.95 $2.70
P10594 24pin $3.95 $3.50
P10596 28pin $3.95 $3.50
Pi0598 40pin $4.95 $4.50

WOW!

WHAT PRICES!

I DC PLUGS &
SOCKETS
WOW! FROM $1.00

D TYPE IDC PLUGS

1-9 104- 100+

• DE9P Spin plug

PI 2166 $1.50 $1.20 $1.00

• DA15P 1 Spin plug

Pi 2168 $1.50 $1.20 $1.00

• DB25P 25 pin plug

Pi2170 $4.50 $3.95 $3.50

D TYPE
IDC SOCKETS
1-9 10+ 100+

• DE9S 9 pin socket

Pi 2167 $1.50 $1.20 $1.00

• DA1SS 15 pin socket

PI2169 $1.50 $1.20 $1.00

• DB25S 15 pin socket
P12171 $4.50 $3.95 $3.50

IDC CENTRONICS 36
WAY PLUG & SOCKET
1-9 10+ 100+

• Plug Pi2200

$3.95 $3.00 $2.95

•Socket P12201

ECONOMY

TRANSFORMERS

2155 240V
M121SS....

2156 240V

M12156_

2851 240V
M12851.......

6672 240V
Ml6672.....

1-9 10+

6-15V 1A

.$8.95 $7.95

6-15V A2

...$13.95 $12.95
12-6VCT 250mA
$4.95 .. $4.50
15 30vc 1A tapped
...$12.95 $11.95

12V DC FANS

80 x 80 x 25.4mm

12V DC. 1.7 Watt 0.14 Amp

T12469.-.$18.95

10+ fans, only $17.95

FANS

Quality fans for use In
power amps, computer
hotspot cooling etc.
Anywhere you need plenty
of air.

240V 4 5/8" T12461 ..$16.95
115V 4 5/8" T12463..$16.95
240V 3 1/2" Tl2465..$16.95
115V 3 1/2" T12467..$16.95

TOGGLE
SWITCHES

1-9 10+

811010 S.P.D.T $1.20 $1.10
S11Q20 D.P.D.T $1.30 $1.20

ICB VOLTAGE
REGULATORS
BARGAINS

lOeaeription 1-9 10+ 100+

'7805UC $0.50 $0.45 $0.40
7812UC $0.50 $0.45 $0.40
7815UC $0.50 $0.45 $0.40
7905UC $0.60 $0.55 $0.50
7912UC $0.60 $0.55 $0.50
7915UC $0.60 $0.55 $0.50
78L05 $0.40 $0.30 $0.28
78L12 $0.40 $0.30 $0.28
LM324 $1.00 $0.90 $0.80
555 $0.40 $0.38 $0.33

741 $0.50 $0.45 $0.39

9 PIN D
SWITCH BOXES

2 WAY....-.$59.95

4 WAY....-.$69.95

MONITOR & KEYBOARD
SWITCH BOXES $69.50

MINIATURE,
HOBBY
VICE

• Lever operated suctl
base grip for instant
mounting & portability.

• Mounts on smooth
non-porous surfaces

• Ideal for holding &
other small objects.

T12458. x .$6.95

BOARD
HOLDER

Better than en ^
extra pair of handa^^r
A must for all PCB work.
T12444.$9.95

QUALITY 3mm LEDS

1-9 1 0-99 100+ IK |

1000 +

Z10140(R) $0.13 $0.12 $0.10 $0.08
Z10141(G).. $0.20 $0.18 $0.15 $0.12
Z10143(Y)„ $0.20 $0.18 $0.15 $0.12
| Z10145(0).. $020 $0.18 $015 $0.12

QUALITY 5mm LEDS

|Z10150(R). $0.15 $0.12 $010 $0.08
Z10151(G). $0.25 $0.20 $018 $0.12
|Z10152(Y) . $025 $0.20 $018 $0.12

FLASHING LEDS
RED 5mm 1-9 10+ 100+ |

|Z 10159 $1.10 $1.00 $0.£

RECTANGULAR
LEDS

1-9 10+ 100+ IK

RED 20c 15c 12C 10c

GREEN 20c 15c 12c 10c

YELLOW 20c 15c 12c 10c

DB25 CONNECTOR
SPECIALS

1-9 10+ 100+

P10880DE9P $1.00 $0.80 $0.60
P10863 DE9S $1.00 $0.70 $0.60
PI0891 0A1SS $1.00 $0.70 $0.60
P10892 DAI SC $1.00 $0.90 $0.60
P10895 DA15S $1.00 $0.80 $0.60
P10902 DB2SC $1.00 $0.80 $0.60
P10904 DB25P $1.00 $0.80 $0.60
P10905 DB258 $1.00 $0.80 $0.60

MOSFET SPECIALS

1-9 10+ 100+

2SJ49 $9.50 $8.00 $7.00

2SJ56 $10.00 $9.50 $8.50

2SK134 $8.50 $8.00 $7.00
2SK176 $9.50 $8.90 $6.90
2SJ50 $9.50 $8.50 $7.00

2SK135 $9.50 $8.50 $7.00

ELECTRET
MIC INSERTS

With pine for eaey board
Ineertion. C10170
1-9 1 0-99 100+ 1000+

$1.20 $1.00 $0.90 $0.70

TRANSISTORS
BUY IN BULK
& SAVE!

1-9 10+ 100+

BC 547 $0.15 $0.10 $0.07
BC 548 $0.15 $0.10 $0.07
BC 549 $0.15 $0.10 $0.07
BC 557 $0.15 $0.10 $0.07
BC 558 $0.15 $0.10 $0.07
BC 559 $0.15 $0.10 $0.07
BC 327 $0.20 $0.15 $0.12
BC 337 $0.20 $0.15 $0.12
BD 139 $0.75 $0.60 $0.50
BD 140 $0.75 $0.60 $0.50

PCB MOUNTING
SCREW TERMINALS

(INTERLOCKING ENDS)
These terminals feature
interlocking ends to form
any number of connections.
Standard 5mm spacing
pins.

P10520 2way

1-9 10_ 100+

$0.75 $0.70 $0.60

P10521 3 way

$1.00 $0.90 $0.80

ARLEC 24 HOUR
MULTIPURPOSE
TIME SWITCH

I Multi-purpose is the key word when
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I wake up or come home to a warm
I or cool house.

I And just think of the advantages of
being able to record radio
programs while your not even
I home.

I This timer switch automatically
| switches appliances
I On & Off up to 24 times each day!
M21900.$35.95

MOTION ACTIVATED
ENTRY ALARM

I A handy little device which
I announces visitors and protects
I property with a loud alarm or soft
I chime when the beam of protection
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I Can also be used for store entries,

I offices, basement stairs and
I garages. Great for providing a
I warning for children around pool
I areas and other places where they
I can be in danger.

| SPECS:

• 9 volt battery required (not
I included)

I • Instant chime: one sound per
I entry

• ALARM: 10 second exit delay after
I turning on.

I • Alarm sounds for 30 seconds
(85db at 3 feet) and then
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• Includes screws,wall anchors and
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1 SI 5074.,...$64.95

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Desktop charger is an optional extra.
TRANSMITTER

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RECEIVER

Sensitivity is more than 1.2dB at
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Similar units sell for $499 ( LCD
Digital readout)

OUR PRICE $295.00

Desk 240V Battery Charger $99..00

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BLASTER

"YOU AIN’T
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The Sound Commander fx is built with an extra socket for you to plug in
another 'YAMAHA FM synthesizer chip to upgrade it to full stereo with
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Karaoke Mixer with Echo Mic input is directed tom the power amplifier for
Karaoke mixing with echo effects
DSP RAM Buffer

8K DSP RAM for PCM digitized sound and MIDI output. Programmable for
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MIDI Interface

Standard UART interface with 8K DSP RAM buffer built-in to connect MIDI
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only $159.00

The Little
Squrit
BJ-10 ex

Printing Speed
High Quaility
High Speed
Print Width
Resolution
Built-in Fonts
Dimentions (w x d x h)
Weight

C22218.

S(.H IK I

sgi lire

SQUIRT

83cps (lOcpi)

83cpe (lOcpi)

203mm

Up to 360 x 360 dpi
Courier, Prestige, Elite
310mm x 216 x 48mm
Approx. 1.8kg AC

.$589.00

BJ300
Bubble Jet
Printer

Printing Speed:
High Quaility
High Speed
Print Width
Resolution
Built-in Fonts

Weight

C22226.

150cps (lOcpi)
300cps (lOcpi)
203mm

Up to 360 x 360 dpi
Courier, Prestige,
Gothic

Approx. 6.9kg

.$1049.00

BJ330
Bubble Jet
Printer

Printing Speed:
High Quaility
High Speed
Print Width
Resolution
Built-in Fonts

Weight

C22227.

~~TTZ,

150cpe (lOcpi)
300cpe (lOcpi)
340mm

Up to 360 x 360 dpi
Courier, Prestige,
Gothic

Approx. 8.8 kg

.$1195.00

ROD IRVING ELECTRONICS

MELBOURNE: 48 A'Beckett St. Ph: (03) 663 6151.
Computer sales: Ph 639 1640. FAX: (03) 639 1641
NORTHCOTE : 425 High St. Ph: (03) 489 8866
FAX: (03) 489 8131

OAKLEIGH: 240C Huntingdale Rd, Ph: (03) 562 8939
SYDNEY: 74 Paramatta Rd. Stanmore. N.S.W.

Ph: (02) 519 3134 or (02) 565 1458, FAX: (02) 516 5024
ADELAIDE: 241-243 Wright St, Adelaide. Ph: (08) 2117200
MAIL ORDER: 56 Renver Rd, Clayton Vic, 3168.

Ph: (03) 543 7877 FAX ORDERS: (03) 543 2648
Mail Order Hotline: Ph: 008 33 5757
DEALERS:BLUESTAR COMPUTERS

(Computer Products only)

MELBOURNE: 217 Maroondah Hwy, Ringwood.

Ph: (03) 870 1800

SYDNEY: 115-117 Parramatta Rd, Concord. Ph: (02) 744 5526

MAIL ORDER & CORRESPONDENCE

P.O BOX 620, CLAYTON, VICTORIA, 3168.

Errors & omissions excepted. Prices & specifications
subject to change. IBM*, PC*, XT*, AT*, are registered
trademarks of International Business Machines. *Apple is a
trademark of Apple Corporation.

Quick G hat

AVIATOR 5

• AUTHENTIC AIRCRAFT
CONTROL YOKE

AUTOMATIC CONTROL
YOKE CENTERING

• COMPATIBLE WITH IBM PC,

XT AT AND 386*

. 4 POSITIVE RESPONSE
FIRE BUTTONS

• REALISTIC ALTITUDE/LEVEL INDICATOR

• 2 DUAL-SPEED TURBO FIRE BUTTONS

• X-AND Y-AXIS TRIM CONTROL SWITCHES
. 6-FOOT CABLE WITH 15-PIN CONNECTOR

• STABILIZING SUCTION CUPS

. 6 U.S MILITARY INSIGNIA STICKERS

Cl 4250.$89.95

• Requires Smart Games Card...Cl4260.$39.95

(YOU HAVE TO USE THESE IN A 386 + 486)

INTRUDER 5

• OMNIDIRECTIONAL GRIP

• COMPATIBLE WITH IBM PC,

XT, AT AND 386*.

• AUTOMATIC CONTROL
STICK CENTERING
. 2 POSTIVE RESPONSE
FIRE BUTTONS
. 2 DUAL-SPEED TURBO
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• POP-UP FIRE BUTTON COVER
. X AND Y- AXIS SWITCHES
. 6-FOOT CABLE WITH 15-PIN CONNECTOR
. STABILIZING SUCTION CUPS

• 6 U.S MILITARY INSIGNIA STICKERS

Cl 4240.$79.95

• Requires Smart Games Card Cl 4260....$39.95

SMART GAMES CARD

SUPPORTS 4.77 TO 80MHz

Complete with Calibration software
FEATURES:

• Intelligent software controlled game card

• Compatible with IBM PC/XT/AT/386/486

• Complete with easy-to-use menu driven calibration
software on 5.25" floppy diskette

• Software selectable clock speed - from 4.77 to 80MHz

• Automatic clock speed adjustment for advanced users

• Hot-key program for fine-tuning clock speed during game

• 2 15-pin joystick port-supports 1 or 2 joysticks operation

Cl 4260.$39.95

STOP PRESS!

ADELAIDE STORE NOW OPEN:
241-243 WRIGHT ST, ADELAIDE.
PH: (08) 211 7200. FAX: (08) 211 7273

Quick G hat

QUICKTRAC 100

A new concept in Mice!

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responsive enough to detect changes without much
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respectively and the key-lock button by your middle
finger.

They're are great for laptops and notebooks or
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100% Microsoft Mouse compatible.

Includes Qtrac™ Driver software
QMenu™ Pop-Up Library
Menu making Utility
DB9 to DB25 Adapter.

System Requirements: Any IBM, PC, XT, AT or
compatible computer
• One 9-pin or 25-pin RS232 serial port.

Cl 4230.$69.95

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INNOVATION!

LAMINATOR^

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Laminate Sheets....95mm x 57mm (2.25” x 3.25")
for business cards

A91110.$18.95 pack of 100

Laminate Sheets....156mm x 112mm (4.25” x 6.75”)
for photo's with punch holes for photo albums
A91111.$11.95 pack of 24

Laminated Sheets....135mm x 95mm (3 3/4"
tor photo's and cards

A91113......$8.95 pack of 24 _

Laminate sheets....110 mm x 170mm (4.25" x 6.25")

A91112.$10.95 pack of 24

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MONITOR STAND

- Fits large monitors with feet
separation up to 10" x 11"

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• Fully adjustable while in use

• Stable 25° tilt 360° turn

• Anti Skid feet

Dll 100 12".$9.95

D11102 14".$12.95

ANTI GLARE SCREEN

Relieve eye strain and
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12" Screen.$9.95

14” Screen.$19.95

NEW POWER
OUTLETS

12 WAY POWER
BOARD

This is the big daddy of them all.

Get the most out of your power
points with this 12 way power
board. Don't kill yousetf by loading
up the power point with Double
adaptors. This is the safe and neat
way to use 12 appliances out of the |
one socket.

Comes with a 1 metre fitted cord
and plug and is rated lOamps,

2400 watts. Also has overload
protection.

PI 8038.$34.95 I

PIGGY BACK
EXTENSION LEADS

This is the new look in extension
leads. Makes other extension
leads look old fashion!

It's a 240 Volt, 10A extension lead
which is fitted with a socket on
one end and a piggy back double
adaptor plug on the other. Turns
your one point power point into
two while giving you the benefit of
an extension cord.

1 Metre Pi8060.$5.95

2 Metre PI8070.$6.95

4 Metre Pi8080.$9.95

/('V

r* \

\ % 4r A

\ J

ADAPTOR”

Unique dual adaptor. More than just I
a double adaptor.

Holds plugs more securely than old |
fashioned double adaptors

• 1 x right handed adaptor

PI 8022.$5.50

• Twin pack with left & right hand
adaptors

P18024../ .$9.95

US/EUROPEAN TO AUST.
MAINS ADAPTOR

Converts any two pin US or
European plug to an Australian
tow pin AC plug
• Designed for use with 240 volt
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P18012....._^ £Sii ....$5.95

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WAND

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Input: 240V 50Hz 2 AMP
Rating: 2 min on 30 min off

T12316.$98.95

RCA’s first TRF receiver

In 1925, the Radio Corporation of America released its first TRF receiver for domestic broadcast
reception. Built by General Electric, the Radiola 20 offered ganged tuning, two RF stages and a
regenerative detector, using a circuit which had similarities to the well-known Browning Drake
design. It provided a high order of performance, for a high but attainable price.

The Radio Corporation of America
was incorporated in October 1919, in a
takeover of American Marconi by a con¬
sortium of General Electric, American
Telephone and Telegraph, Westinghouse,
and the Wireless Specialty Apparatus
Co. Between them the consortium mem¬
bers held not only the very important
Armstrong Regeneration and Superhet¬
erodyne patent rights, but also they con¬
trolled just about every other major radio
patent — which other manufacturers
could not use without an RCA licence.

With close affiliations to overseas or¬
ganisations (Australia’s Amalgamated
Wireless being a case in point), RCA had
access to worldwide developments. This,
together with their patent monopoly,
gave them the potential to be the world’s

leader in radio technology. It is important
to realise that prior to 1930 RCA had no
manufacturing facilities of its own, but
concentrated on operating and on mar¬
keting products made by its principals.

An interesting situation arose here.
AWA were the agents for RCA receivers
sold in New Zealand, but because AWA
made their own receivers, often with a
strong RCA influence — even to the ex¬
tent of taking over the name ‘Radiola’ —
Australian RCA imports were handled
by Australian General Electric until
1930, when import restrictions cut them
out altogether. RCA sets sold in Australia
could not display the name ‘Radiola’.

Initially, RCA had not been keen to
become involved in the broadcasting
craze, which they had regarded as

Fig. 1 (above): This table model version
of the RCA 20 has an overall black
cabinet made by the Salt-Smith Trust
of Salem, Indiana.

Fig.2 (left): The more common finish
was natural wood with black stained
borders , as shown on this floor model
— which incorporates a battery box
made by the Jamestown Mantel Co.
Note the optional plug-in filament volt¬
meter to the right of the four lower
controls.

ephemeral. But when it became clear
that broadcasting would not go away, it
began selling receivers designed and
built by GE, Westinghouse and WS A.

RCA did not exploit its very powerful
position effectively. Although by late
1925 the US industry’s ‘standard’ re¬
ceiver consisted of two RF stages, a de¬
tector and two audio stages, no RCA
radios had previously been of this type.

For various reasons, including previ¬
ous overproduction, the company had
not made regular annual model changes,
and consequently, for the 1925-26 sea¬
son, they had an odd range of receivers
on offer. Some was old stock, the ‘bot¬
tom of the line’ model being the primi¬
tive two valve variometer-tuned
regenerative Westinghouse Radiola HI
— discounted to only $15. Then there
was the 1924 ‘first generation
superheterodyne’ from GE, reduced to
$116 but still expensive.

With one exception, all the new 1925
RCA models were superheterodynes,
ranging from the $195 model 24 to a
stratospheric $575 for the model 30.
Comparative rates are not available, but
it would not be unreasonable to multiply
these prices by a factor of 10 for a guide
to today’s values.

RCA needed a current model that was
priced more competitively. Their answer
was the Radiola model 20 TRF, priced at
$102.50 but still in the upper price range.
To quote two examples, this was nearly
60% dearer than the equivalent $65
Stewart Warner 300, described in this
column for May 1991, and 30% more
than the 20C Atwater Kent. To be fair
though, the RCA 20 was a more complex
and higher performance receiver.

High price, quality

The cabinet styling and internal con¬
struction of the RCA 20 reflect the ‘up
market’ character of RCA receivers.

104

ELECTRONICS Australia, October 1992

The schematic for the RCA 20. No values are given for the three fixed
capacitors, but the HT bypass Is known to be 2uF and suitable bypass
values for the detector grid leak and anode are250pF. The grid leak resistor
is not critical, and can be any value between 1M and 3M. The regeneration
howl suppressor resistor across the primary of the first audio transformer
Is typically 100k.

RAOIO CORP. OF AMERICA

NATIONAL SERVICE DIVISION

133 EROAOWAY. N. V. C.

RADIOL A 20

SCHEMATIC DIAGRAM

Dwg No.NS-20-1 Date II-2S-I975

Own. By HIS. Ickd.By 1 *’ 8 | Appd. By

Whereas the average 1925 receiver was
pretty functional, comprising a rectangu¬
lar box with a front panel featuring three
large tuning knobs, two smaller filament
control knobs and the odd switch, RCA
receivers were more ornate, with some
attempt to look like a piece of furniture.

All the 1925 RCA receivers had sim¬
ilar cabinets featuring a sloping front
panel, lift-up lid and and elaborate routed
decoration on the front and sides. As can
be seen from the photographs, there were
two Model 20 colour options, one being
all black and the other two-toned, with
black edgings around polished wood en¬
closed within the routed patterns.

The main panel was sloped at a 45°
angle, with two large thumbwheel con¬
trols and ornate brass escutcheons. One,
as would be expected, was the tuning
control — in this case labelled ‘station
selector’ — but the other one, called
‘amplification’, was not a volume con¬
trol. It was in fact a regeneration control,
working through a linkage to adjust a
feedback or ‘tickler’ winding.

Ganged tuning

A significant feature of the RCA 20
was ganged tuning. Until about 1927, the
standard TRF had three tuning controls,
creating difficulties for users who did not
have three hands! The problem was well
recognised, but aerial coupling methods
and tolerances between tuning capacitors
made ganging very difficult.

Although RCA was not the earliest to
use single knob tuning, its model 20 can
be regarded was the first really success¬
ful receiver to feature ganging. Even so,
it was necessary for the trimmers to be
manually operated. (Readers of last
month’s column will hopefully recall
that Majestic receivers still used aerial
trimming in 1930.)

The model 20 was therefore RCA’s
first conventional TRF, and it proved to
have excellent performance, incorporat¬
ing two triode RF amplifiers — neu¬
tralised for optimum gain and stability
— and with regeneration for high gain
and selective detection.

Although popular here and in Europe,

Fig.3: Only an ornate embossed brass
badge was good enough for RCA. To
avoid conflict with A WA 's rights to the
name ‘Radiola’, badges on sets
intended for Australia had the name
altered to Radio 20.

and for home construction, regeneration
was used by few American makers,
doubtless because royalties were payable
to RCA and many users had difficulties
with yet another control.

The inevitable two transformer-cou¬
pled audio stages completed a generally
tidy design.

Late in 1924, G.H. Browning had de¬
scribed a sensitive receiver that was to
become very popular with home con¬
structors right through to the 1930’s.
Special features of the Browning Drake,
as the circuit became known, were a neu¬
tralised RF stage, and regeneration con¬
trolled by a moveable feedback winding.
Add a second RF stage to a Browning
Drake circuit, and you have the essen¬
tials of the RCA 20.

We will never know for sure, but one
could speculate that the GE design team
who, after all, had not previously pro¬
duced a TRF, had studied Browning’s
design and built on it...

Unusual construction

At this period of development, the
usual internal construction of radios was
for components to be mounted on a shelf
or baseboard. But the RCA method was
quite different, perhaps reflecting the
communications and electrical engineer¬
ing background of General Electric.

The model 20 receiver was built
around a more or less triangular frame.
Through the centre was a resilient rubber

ELECTRONICS Australia, October 1992

105

and spring-mounted bakelite moulding,
carrying valve sockets and mountings for
the audio transformers and three RF
coils. At the rear was a terminal board
and a pair of neutralising capacitors. A
pair of carbon resistors, a 2uF HT bypass
capacitor and two mica capacitors
rounded off the parts list.

On the front of the frame was the main
sloping panel, backed by a metal plate
carrying the three tuning capacitors and
the regeneration control. Two filament
rheostats and two three-plate variable ca¬
pacitors (used as trimmers) together with
a pair of phone jacks, were mounted on a
narrow vertical wooden strip at the bot¬
tom front. Also on this strip were two pin
jacks for monitoring the filament voltage
using an optional plug-in voltmeter.

There was no shielding for the three
RF coils. Instead, they were mounted
mutually at right angles to avoid cou¬
pling. A complication of the neutralisa¬
tion was the need for tappings on the
tuning coils, and isolation of the tuning
capacitor rotors by insulated flexible
couplings.

The whole assembly of frame and pan¬
els fitted neatly into the cabinet, to be
secured by four screws on the underside.

Dry battery power

As is well known, the standard Ameri¬
can valve used in the vast majority of
receivers during the mid 1920’s was the
201A, featured in our April 1991 col¬
umn. The filaments of a set of 201A
valves drew 1.25 amperes, from a messy
6-volt lead acid battery which threatened

Valve

Electronics

|i Sales Repairs Restoration
|f and Overhaul of:

| valve radios — audio
§ gear — instrumentation.

|l Twelve month written
iji wairanty on all work.

| We also sell, buy, swap,

| and trade parts and/or
1? complete sets.

(VINTAGE
WIIKELIESS^

lilll 4 4

w I 60 Australia St
< It Camper down NSW 2050
£ | Australia 02 557 2212 j|

Fig A: In this rear view of the chassis, the detector coil with its primary mounted
inside on three spacers is visible at lower left. The set's three coils are mounted
mutually at right angles, underneath the sprung valve deck.

to rot everything in the near vicinity and
also required frequent recharging.

Although it was a most successful GE
development, few RCA receivers used
the 201 A. They preferred instead the 3.3-
volt 60mA filament general purpose type
199 and the 132mA filament type 120
output valves, and for the RCA 20 rec¬
ommended a filament battery of a 4.5
volt series-parallel combination of six
No.6 dry cells.

These would have increased running
costs, but customers who were prepared
to pay the higher prices for RCA receiv¬
ers were probably quite happy to pay

Discovering

VINTAGE

RADIO

Enjoy reading about vintage radio?

If so, you’ll enjoy reading Peter
Lankshear’s new book. We’ve col¬
lected together 34 of his most popular
articles on the subject, and reprinted
them to form a highly readable intro¬
duction to this fascinating subject.

Now available for only $4.95 from
your newsagent — or by mail from
Federal Publishing, PO Box 199, Al¬
exandria 2015. If ordering by mail,
add $2 to cover packing and post.

extra for the convenience of having dry
batteries for the filament supply.

The 20 in operation

Ganged tuning does make operation of
the RCA 20 simpler than its contempo¬
raries, but even so, some skills have to be
developed for good results. By later stan¬
dards, regeneration control is not very
smooth and the thermal inertia of the
filaments delays the response to adjust¬
ment of the gain control.

The tuning control is not calibrated in
frequency, but has a surface suitable for
pencil marking of station locations. As
tuning is varied, a small amount of trim¬
mer readjustment is required.

As would be expected, with controls
adjusted correctly, and connected to a
reasonable aerial, the 20 is better than its
contemporaries and is comparable with
some modem receivers. In a suburban
location, the limiting factor is back¬
ground noise.

The number of surviving RCA 20 re¬
ceivers rescued by collectors shows that
it was a durable receiver. Although not
common here, two of the RCA Victor
‘Alhambra’ models and some Canadian
Westinghouse receivers were based on
the model 20, which proved to be popu¬
lar and it remained in production until
late 1927 — by which time it had be¬
come a floor model, with a new and
larger cabinet.

Next month we will describe some res¬
toration procedures for this and similar
receivers. ❖

’

SOFTWARE I COMPUTER

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SERVICES

AUSTRALIA WIDE

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SYSTEMS

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TITLES INCLUDE:

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AUTHORISED SERVICING ON: COMPAQ, ZENITH, & MOST MAJOR BRANDS

FOR MORE INFORMATION CALL

26 FULTON STREET OAKLEIGH SOUTH VICTORIA 3167
TEL: (03) 562 9900 • FAX (03) 562 9615

READER INFO NO. 25

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OCTOBER SPECIALS FROM JAYCAR

REMOTE CONTROL SWITCH

(Wireless Receiver / Transmitter)

At last a quality Remote Control unit with two transmitters for
under $ 100 !

The Transmitters

The keyfobs have two buttons on them, one LOCK and one
UNLOCK with a LED to show unit has transmitted. Size is normal
keyfob size 60 x 35 x 14mm and has a keyring.

The Receiver

It's a black box with a 4 way terminal block for external
connections. These are for +12V, -12V, LOCK and UNLOCK.

Features

There are separate outputs for lock and unlock which are both
momentary (approx 0.5 seconds). There are two separate relays,
one for lock and the other for unlock, which will switch currents
up to 2 amps which is adequate for most applications. There is
also a switch which allows the output relays to switch either to

ground or to +12V to an external control circuit. Both transmitters
and receiver have DIP switches for coding. There are 6,561
different codings available. Remote control range is 28 metres.
Ideal for controlling central door locking, car alarms, etc., etc.,
etc. Supplied with two transmitters and one receiver.

Cat. LR-8822 i-

$79.95 NEW from Jaycar

MAGNAVOX12" WOOFER
MADNESS

Another scoop purchase. About 1/2 price.

Magnavox 12J is a 12* woofer with a black cardboard cone
and foam surround.

Specifications
Power Handling
Resonant Frequency
Frequency Response
Voice Coil Dia.

Sensitivity
Magnet Weight
Cat. CW-2126

BARGAIN PRICE $25 eo

60W RMS program
30Hz ^

30-6000Hz
25mm

87dB IWImt / .

190 grams

lAS

THE WORLD OF SATELLITE TV By Mark Long and Jeff Keating

This book provides everything you’ll need to know about selecting, installing, operating, and
maintaining your own satellite TV system. DBS, digital video compression, HDTV, and other
innovations coming your way are also presented in a down-to-earth style that is accessible to
everyone. The World of Satellite TV, with its maps, charts, and satellite “footprints" should serve |
as a valuable addition to the library of both newcomers and experienced satellite TV viewers.

Also included is information on satellite TV in Australia, and footprint maps and transponder
allocation charts for all satellites in the region.

222 pages, softcover 246 x 187mm. Cat. BC-1145 $34.95

The World of
SATELLITE TV

CRO MADNESS

Save 20% on 6.4MHz CRO

Cat. QC-1910

Normally $399
OCTOBER $319.20

Save 10% on 20MHz CRO

Cat. QC-1900

Normally $699 OCTOBER $629.10

See catalogue tor full details. Probes are extra. Cat. QC-1910 use QC-1912 $45. Cat. QC-
1900 use QC-1902 $39.50 ea.

Cat. QC-1900

THE 12 VOLT BIBLE FOR BOATS

By M. Brotherton

This book is a nuts and bolts primer on 12 volt electrical systems
for boat owners who are not skilled electricians. It’s also ideal for
anybody interested in 12 volt

power systems. Chapters
include: Basic Theory of
Electricity, Electric Circuits,
The Battery, Wiring, Controls
(switches, fuses, meters, etc)
Transducers (lights, motors,
pumps, fridges,
consumption, etc.),
Recharging the Battery,
Troubleshooting.

174 pages, softcover, 147 x

230mm

Cat. BT-1342

$28.95

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didLE

FOR BOATS

MINER BROTH f.RYON

BUILD THIS NiCAD BATTERY DIS¬
CHARGER KIT

REF: SC JULY 92. This battery discharger is specifically designed
for video camera or mobile telephone batteries. It can be set for
different types of
batteries from 6-12V and
will save you money by
reviving that dud battery.

This circuit is powered
by the battery under
discharge and, therefore,
doesn’t require a
plugpack, making it
completely portable. The
Jaycar kit is supplied
with diecast box, PCB
and all specified
components.

Cat KC-5120

$27.95

{ HEAVY DUTY 75Q COAX

CABLE MADNESS

We’ve bought a quantity of quality 75Q coax from a large
company because their purchasing dept ordered white instead
of black. This coax is basically the
same as our WB-2004 heavy duty
coax which sells for $1 metre or
$70 per lOOmt roll. Because it’s
white we’ve halved the roll price.
SPECIFICATIONS
Conductor - solid 1/0.70mm.
Overall diameter - 7.3mm.
Screening AI/Polyester/AI tape
0.05mm. Braiding 0.16mm PACW.
Resistance - 44.8fi/Km.
Capacitance at 1 kHz 67pF/m.
Attenuation -13dB/100m max.

Cat. WB-2005

ONLY $35 per 100 metre roll

60 $ per metre in smaller than roll quantities.

SAVE $25 ON DMM WITH
EVERYTHING
TES Multimeter

3.75 digit

4000 count, 39 range.

Inductance, capacitance,
frequency, temperature,
logic, peak hold, data
hold, 20A
Cat. QM-1475

WAS $169
NOW
$144

Dolby Surround Sound Decoder Kit

Ref: EA January 1992. Experience cinema sound in your own lounge room. The Dolby 'Surround Sound' process increases the sensation of 'being there' by producing an effects channel to create
surround sounds which a conventronals stereo system can't produce. Hook this simple kit in conjunction with your Hi Fi VCR or stereo TV and take full advantage of movies recorded with Dolby encoding
Short form kit - includes PCB, and all on board components. Cat. KA-1741 ^5

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ONICS
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HOOK-UP WIRE/AUTO CABLE
SAVE $3 per pack in OCTOBER

Don’t miss this
opportunity to stock
up with quality cable
at crazy crazy low
prices. We’ve bought
thousands of packs of
Arista cable, and you
can save a fortune.

There are 5 different
sizes and colours of
each size. All the

cable is packaged in _

blister packs. They are available in large packs of one roll each
colour. One large pack for each cable size.

HUW5

14/0.25mm, 18 gauge OD 2.4mm. Black, green, red, white,
yellow. 12 metres per colour. Total length 60 metres. Arista
catalogue price $5.95 per colour. Total $29.75

Cat. wh-3019 WAS $12.95 NOW $9.95

HUW6

10 amp hook-up wire. Size 16 x 0.3 = 4.8mm. OD 2.6mm. 16

gauge. This is equivalent to our WH-3040 heavy duty hook-up
wire. 8.6 metres of each colour. Total length 43 metres, 5
colours. Arista price $29.75

Cat. WH -3020 WAS $10.95 NOW $7.95

HUW7

12 amp hook-up wire. Size 19 x 0.36 = 6.8mm. OD 2.9mm. 14
gauge. This is equivalent to our WH-3050 extra heavy duty
i hook-up wire. 6 metres of each colour. Total length 30 metres,
15 colours. Arista price $29.75
Icat WH-3021 WAS $9.95 NOW $6.95

HUW8

15 amp auto cable. Size 19 x 0.45 = 8.55mm. OD 3.5mm. 12
gauge. This is equivalent to about 4mm auto cable. 3.6 metres
of each colour. Total length 13 metres, 5 colours. Arista price
$2975

cat WH 3022WAS $9.95 NOW $6.95

HUW9

25 amp auto cable. Size 19 x 0.59 = 11.21mm. OD 4.4mm. 10
gauge. Suitable for the heaviest jobs. 2.4 metres of each
colour. Total length 12 metres, 5 colours. Arista price $29.75
cat WH 3023 WAS $7.95 NOW $4.95

BUY 10 - LESS 10%

SEMICON'S TRANSISTOR INDEX
(DATA & EQUIVALENTS) This book

represents an absolute bargain considering the data it contains. A
huge data book listing data for thousands of transistors, as well as
a large equivalent section. The book is designed for the Engineer
and Technician. Section 2 lists manufacturers names and addresses

• Section 3 is the huge
alphanumeric listing of
transistors with specifications •

Section 4 lists FETs with specs •

Section 5 covers unijunction
transistors • Section 6 is the
substitution guide • Section 7
covers devices with the prefix CV

• Section 8 lists 100’s of
transistor outline drawings and
terminations.

591 pages Size 242 x 170mm
Cat. BM-2477

$19.95

' SEMICON S ’ ‘
" INTERNATIONAL *
TRANSISTOR INDEX

* . i ■ •

BIT-MAPPED GRAPHICS

By Steve Rimmer
A programmers’ guide to
understanding and using the most
popular IBM PC and Macintosh
graphics files formats. Featuring
plenty of ready to use source code
and bit-mapped graphics
illustrations. You’ll learn how to:

• Navigate through MacPaint,

GEM/IMG, PC paintbrush, GIF, and
TIFF graphics file formats • Use
different types of graphics drivers -
including Hercules, CGA, EGA, and
VGA • Reproduce graphics on
LaserJet, dot matrix and PostScript printers • Create bit-mapped
graphics with object-oriented programming techniques • Use
dithering and other algorithmic image manipulation methods.
Softcover, 492 pages 234 x 187mm

Cat. BT-1344 $59.95
ADVANCED BATCH FILE
PROGRAMMING

3rd Edition by Dan Gookin
You’ll learn about • DOS
commands and syntax • Batch file
programming tools and techniques

• Customising CONFIG.SYS and
AUTOEXEC.BAT • Macros and
control languages for popular
applications • Writing and
troubleshooting interactive batch
files • Improving batch files with
BASIC, EBL, Builder and Beyond-
Bat • Programming batch files in

j OS/2 • Sample programs and a
complete batch file cookbook.

Covers DOS 3,4 and 5. “A goldmine of shortcuts, tricks and
| techniques in using batch files". Computer Shoppers.

499 pages, softcover, 234 x 187mm. Includes disk.

Cat. BT-1346 $65.95

MS-DOS BATCH FILE
PROGRAMMING

3rd Edition by Ronny Richardson
This book teaches you the latest approaches and techniques for
writing batch files, including programs that add password
protection, solve parameter problems, load and manage TSR
applications, change system configurations, and much more. With
the batch files found here, you’ll be able to build:

• Your own menu system to handle all your programs • A

complete document archive system
to prevent losing important data files

• A library of batch files to protect
your computer from viruses •

Customise AUTOEXEC.BAT and
CONFIG.SYS files • BASIC
programs to beef up your batch files

• Patches to the operating system
using DEBUG and Norton Utilities.

Includes DOS 3,4 and 5.410 pages,

234 x187mm Includes disk.

Cat. BT-1348 $59.95
UPGRADE YOUR
IBM COMPATIBLE
AND SAVE A
BUNDLE

2nd Edition by Aubrey Pilgram
Don’t buy a new computer, upgrade!

This book offers you step-by-step,
illustrated instructions show you
exactly how to: • Replace original
motherboards with 80286,80386 and |

80486 processors • Add new floppy
and ha[d disk drives • Install BIOS
and RAM chips, graphics cards and
memory fax, and network boards • Plug in state-of-the-art
monitors, laser printers, modems, input devices, and other
peripherals. If you know how to
handle a screwdriver, you can have |
all these enhancements and more
for a fraction of the cost of buying
a brand-new PC.

245 pages 232 x 185mm

Cat. BT-1350 $44.95

ENCYCLOPEDIA
OF ELECTRONIC
CIRCUITS

VOLUME 4 _

This fourth Edition offers you hundreds of all new schematics for
the most up-to-date electronic circuits, straight from the drawing
boards of industry leaders such as Motorola, Texas, National etc.
There are 104 chapters from Active Antennas to Wireless
Microphones. Most of the circuits have appeared in publications
since 1988. There are literally 100’s of circuits and most use
common garden variety components.

Soft cover, 729 pages 234 x 187mm

Cat. BT-1352 $69.95

DOS BEYOND
640k

2nd Edition by James Forney
This book has it all for RAM
restricted DOS users. Includes
• the 80486 processor •

Windows multitasking •

VM/386 and DESQ view •

Alternate operating systems
such as PC-MOS/386 • XMS
memory management
techniques • Extended
Industry Standard Architecture
(EISA) • High speed multitasking software for the 8088 • DOS 5
and DR DOS 5 • Running Lotus 1-2-3 and WordPerfect with
extended expanded memory. Also explained is how you can
access memory installed above DOS’s 1Mb ceiling, and how to
use memory in the 640k -1 Mb region that, although reserved by
the system actually is not used by DOS.

Softcover, 283 pages 234 x 186mm

Cat. BT-1354 $49.95

COMPLETE BOOK OF
OSCILLOSCOPES

2nd Edition by Stan Prentiss

This book examines in detail virtually every aspect of CROs and
their use, including advanced
testing procedures: • Digital
storage CROs • spectrum
analysers (from DC to 21 GHz) •
logic and signature analysers •
metal cable and fibreoptics time
domain reflectometry • storage
and A/D/A converters • GPIB,

RS-232 and future BUS
instrument connectors • digital
printers and much more. If you
work with CROs for any
experimental or troubleshooting
purpose, you’ll need this book.

Softcover, 305 pages 233 x
187mm

Cat. BT-1356 $37.95

the complete book of

OSCILLOSCOPES

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/tflGH QUALITY EDGE METER BARGAIN

This meter is a high quality Japanese made edge meter.

It is a 100V AC FSD moving coil type. It can easily be changed into an Amp or
Milliamp meter by using a shunt resistor. The meter scale is blank, so you
can easily put your own scale on it. Size: Front bezel 73(W) x 25mm.

Panel cutout 58(W) x 18mm. Depth from front panel 63mm. Height at
rear 34mm. To buy these today you would pay around $30 - $35

.Cat. qp 5060 OUR PRICE $14.95

THE BIGGEST TV ANTENNA

This is the biggest antenna we have ever seen. It's an extremely high
gain UHF/VHF/FM antenna for outer metropolitan areas where
signal reception is deep fringe. Includes 75 ohm balun. Also
suitable for metropolitan areas where multiple outlets are required.
Boom length is 2.9m.Cat. LT-3155 $199 50

2 COMPUTER/1 PRINTER AUTO SWITCH

This is a non-power auto data switch designed for using one printer on two computers. No need to
switch, does so automatically and uses no power. Time out 5-6 seconds, provides “Release” signal
for the PC to avoid “Lock" problem when the other PC is printing. Suitable for IBM compatible
systems. Cat. XC-5088 $69 95

QUALITY DISCS
AT SILLY PRICES

5 1/4" DSDD Cat. XC-4730

$5.50 pkt 10
5 1/4" DSHD Cat XC 4732

$10.50 pkt 10

3 1/2" DSDD Cat. xc-4736 $9.75 pkt 10
3 1/2" DSDH Cat.xc-4738 $15.95 pkt 10

Sub C NiCad

Repair your battery pack for RC
cars and power tools with Sub
C's. Ours are the lowest price too!
1.2Ah

.Cat.SB-2456 $6.95

STUDIO 3-55L SPEAKER SALE

12“ 3 way speaker kit
incorporating Magnavox
12w woofer, midrange
and Philips dome tweeter.

Power handling 50 watts
programme. Cabinets are
black and fully built. See
the 1992 catalogue for
full details.

Cat. No(s). CS-2480/2

NORMALLY
$499

OCTOBER
$449
SAVE $50

TURN YOUR SURPLUS STOCK
INTO CASH!

Jaycar will purchase your surplus stocks of
components and equipment. We are continually on the
lookout for sources of
prime quality merchandise.

Call Mark Harris or Bruce Routley
now

(02) 743 5222

9V RECHARGEABLE
Normally $19.95
October $16.95 cat. no. sb-2458

EXTENDED TRADING HOURS FOR
YORK ST STORE

For your convenience now open
Mon-Fri 8.30am to 6.30pm.
Thurs till 8.30pm. Sat 9 - 4pm

FANTASTIC PRICES

120mm 240V

Cat. YX-2514

Catalogue Price
$27.50

NOW
$17.50
SAVE $10
80mm 115V AC

Buy 2, connect in series to 240V and get double the exhaust volume.
Cat. YX-2520

SPECIAL PRICE $10
NOW $7.50 SAVE $2.50

/Answering machine /data ^

CASSETTES

Another surplus deal to save you lots of money. This time its
Maxell brand data cassettes. These are high quality Japanese
made DC-300. We originally thought they were 300 minutes,
because the window has a lot of tape showing. Upon further
checking we found them to be 60 minutes, 30 minutes per side
- and these use high quality thick tape. These are ideal for
answering machines, computer data, etc. We’ve seen these in
catalogues for $8.95 each.

Cat. AR-1470

JAYCAR PRICE
$1.95 ea
Box oMOfor $15

5A DRILL SPEED
CONTROLLER KIT iffy

Ref: Silicon Chip September '92

This new speed controller can be used with power tools rated up
to 5 amps. It can be used to control the speed of circular saws,
electric drills, lawn edgers and other appliances with universal
“brush type" motors. The Jaycar kit is supplied with a jiffy box,
PCB, surface mount mains socket and components.

Cat. KC-5123 $39 95

/DATACE DISKS
100% ERROR FREE

At last. High quality disks without the high quality price.

We had these disks independantly tested and they consistently
outperformed that other expansive brand we used to stock. The
Bit dropout was up to 30% less! Call into any store for your
copy of the report. After the quality, the next best thing is the

price.

5.25"

DSDD

$9.95

Cat. XC-4740

5.25"

DSHD

$14.95

Cat. XC-4742

3.5"

DSDD

$14.95

Cal XC-4746

3.5"

DSHD

$23.95

Cat. XC-4748

MOTOR SIREN

This 12 volt motor driven siren really lets out a
blast. It’s very small compared to most sirens
measuring only 82(H) x 80(L) x 74(D)mm. Limited
quantity.

Cat. LA-5252 WAS $24.95

NOW $19.95 SAVE $5

CABLE TIES IN 100'S
100mm $4.95 cat. HP -1203

150mm $8.95 cat HP -1204
200mm $9.95 cat hp -1205

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10% OFF 6V GEL BATTERIES

1Ah Was $8.95 NOW $8.05

Cat. SB-2479

6Ah Was $14.95
NOW $13.46

Cat. SB-2477

8Ah Was $16.95
NOW $15.25

Cat. SB-2478

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STEREO SPEAKER PROTECTOR

Ref: EA October 1992

This small module will save your expensive loudspeakers from
damage due to an amplifier fault or destructive drive signals. It
includes an “intelligent" de-thump circuit and can be either built
into an existing amplifier or housed on its own. Kit includes
PCB, relay and all specified components excluding extra power

supply parts. Cat. KA-1745 $29.95

SAVE ON CELLULAR PHONE BATTERY
ELIMINATORS When you are in your car, use
your car power and save your telephone batteries. Simply slide the
battery pack out of the phone, and replace it with the Eliminator. It
has a curly cord attached with a cigarette lighter plug.

Cat. MP-3110 Motorola Micro Tac • Cat. MP-3112 Novatel
PTR800 • Cat. MP-3116 NEC P300 • Cat. MP-3114
Motorola 9800/9500

WAS $59.95 OCTOBER SPECIAL $39.95
SAVE $20 on each item

HEAVY DUTY HOT LINE FILTER

Huge 20 amp current capacity. Ideal for high power amplifiers in car
audio systems. Virtually eliminates ignition noise via the resistive
lead to battery. Complete with capacitor and wi ring instructions.
Inductance 0.5mH. ^

Cat AA-3075 NORMALLY $14.95 A

OCTOBER $9.95

SAVE $5

8" TWINCONE SPEAKER SALE

Ideal for multispeaker sound reinforcement where 4 ohm
speakers are required. Quality speaker made in New Zealand.
Limited quantity. 10 watt power handling. Frequency range 60 -
15kHz. Cat. CE-2322 Catalogue price $9.95

NOW $6.95 SAVE $3
WHITE CONE
MIDRANGE
SLASHED

A quality midrange with a sealed back and foam surround. Huge
lOoz magnet makes it efficient and gives good midrange
reproduction. As used in the Studio 3-55L speaker kit.

Power Handling 80W RMS system
Frequency Response 350Hz - 5.5kHz
Resonant Frequency 350Hz
Sensitivity 94dB

Cat. CM-2080

Normally $28.50

NOW $20
SAVE $8.50

SCOPE ALARM KEYPAD SALE

If you’ve bought a Scope 6
alarm from us (or are going
to), don’t miss this.

Intelligent remote keypad to
arm/disarm and program
the system. 7 segment
readout, use up to 3 per
alarm.

Cat. LA-5183

WERE $49.95

NOW $20
SAVE $29.95

TOWER DATA BOOKS:
SELLOUT

Sadly, we can no longer buy Towers books at the prices we were
paying. So, we’ve slashed the prices to clear the final stock out.
See catalogue for full details.

IC SUBSTITUTION MANUAL

Cat BM 4552 WAS $49.95 NOW $34.95 SAVE $15

TRANSISTOR SELECTOR

Cat BM-4554 WAS $35 NOW

$30 SAVE $5

OP AMP &
LINEAR IC
SELECTOR

Cat. BM-4556 WAS

$29.95 NOW
$17.95 SAVE $12

DIGITAL IC SELECTOR

Cat BM 4558 WAS $29.95 NOW $14.95 SAVE $15

DIODE & SCR INDEX • NEW EDITION

Cat BM 4560 WAS $39.95 NOW $24.95 SAVE $15

MICROPROCESSOR SELECTOR

Cat BM 4564 WAS $12.95 NOW $8.95 SAVE $4

AT LAST - THE ECONOMICAL
WAY TO STORE RESISTORS

These trays have 36 compartments and are designed to accept

12V 1)C - 240V AC
INVERTED - NEW MODEL

Now ultra reliable. Features
include: • Low battery alarm
- an audible buzzer sounds
when battery voltage drops to
10.7 volts • Low battery
shutdown - activated when
battery discharges to 10.0
volts, which prevents damage
to battery • Electronic
circuitry protection - prevents
potential damage from
overloads and inadequate
ventilation • High surge
current capability - starts

difficult loads such as lamps, motors and inductive loads.

See catalogue for full specifications.

Cat. MI-5030

Catalogue price $189.50
OCTOBER PRICE $159.50 SAVE $30

1/4 or 1/2 watt resistors. There is space beside each
compartment to write in texta the value of each resistor. If more
than one tray is required they will stack inside each other - so you
can find a resistor - or capacitor, or nut, bolt, etc in a jiffy. We
have sold thousands of assorted resistor packs over the years.
One popular pack being the RR-1697 which has 85 different
values (10 of each value).

To store this pack in these trays you will need 3 (36 x 3 =108)
and you’ll have 23 compartments free for other parts. The size of
each tray is 395 x 260 x 20mm deep. We think they are a great
idea.

Cat HB-6340 $6.50 63

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ELECTRONICS

HEAD OFFICE

6 Leeds Street Rhodes 2138

Telephone (02) 743 5222
FAX (02) 743 2066

POST & PACKING

$10-$24.99 $3.75

$25 - $49.99 $4.50

$50-$99.99 $6.50

OVER $100 $8.00

MAIL ORDERS

P.O. Box 185 Concord 2137

ROAD FREIGHT ANYWHERE IN
AUSTRALIA (up to 20kg) $14.00

MAIL ORDER VIA HT

FREE CALL - FOR ORDERS ONLY

(008) 022 888
HOTLINE (02) 743 6144

ADELAIDE SA

BURANDA QLD

COBURG VIC

5 Z&S

190 Wright St (Cnr. Selby St) (08) 231 7355

Fax (08) 231 7314 Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 -12
144 Logan Rd (07) 393 0777 Fax (07) 393 0045
Mon-Fri 9 - 5.30 Thurs 8.30 - Sat 9 - 4
266 Sydney Rd (03) 3841811 Fax (03) 384 0061
Mon-Fri 9-5.30 Fri 8.30 - Sat 9 - 4
MELBOURNE CITY Shop 2,45 A'Beckett St City (03) 663 2030

Fax (03) 6631198 Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 - 2
SPRINGVALE VIC 887-889 Springvale Rd Mulgrave (03) 547 1022
Fax (03) 547 1046

Nr Cnr. Dandenong Rd Mon-Fri 9-5.30 Fri 8.30 - Sat 9 - 2
SYDNEY ■ CITY 129 York St. (02) 2671614 Fax (02) 2671951
Mon-Fri 8.30 -6.30 Thurs 8.30pm - Sat 9 - 4

BANKSTOWN

GORE HILL

PARRAMATTA

PENRITH

RHODES

363 Hume Hwy Cnr Meredith St (02) 709 2822

Fax (02) 709 2007

Mon-Fri 9 - 5.30 Thurs 8.30pm - Sat 9 - 4 - Sun 10 - 4pm
188 Pacific Hwy (Cnr. Bellevue Ave) (02) 439 4799
Fax (02)439 4895

Mon-Fri 9 - 5.30 Thurs 8.30 - Sat 9 - 4pm

355 Church St (Cnr. Victoria Rd) (02) 683 3377

Fax (02) 683 3628 Mon-Fri 9 - 5.30 Thurs 8.30pm - Sat 9

-4pm Sunday 10am-4pm

199 High St (047) 21 8337 Fax (047) 21 8935

Mon-Fri 9-5.30 Thurs 8.30 - Sat 9-4pm Sun10-4pm

6 Leeds St (02) 743 5222 Fax (02) 743 2066

Mon-Fri 9 - 5.30_

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Information

Conducted by Peter Phillips

centre

Looking further ahead into the digital future

This time around we get a glimpse of what could be a most interesting project, examine a few reader
hassles with existing ones and discuss the Scott connection. To keep you busy, there are also two
What?? questions this month — although you’re really on your own with one of them.

Today’s audio technology is largely
centred around digital devices, particularly
the CD player. While most of us own one,
and probably enjoy it immensely, there is a
growing band of enthusiasts wanting to
‘get at’ the data from a CD. Many CD
players have a subcode output, and some
have other outputs that are not really ex¬
plained in the manual for the player.

An emerging field is DSP (digital signal
processing), and ICs that can do incredible
things with digital audio are now becom¬
ing available. One of our regular cor¬
respondents (G.L., Ringwood Vic) who
first raised a few questions about CD sub¬
codes last year, suggests that ‘DSP will
become the buzzword of the 90’s, just as
digital was in the 80s and solid state was
before that’.

He also reckons that DAFT F A
(pronounced day-leer), an acronym for
Dynamic Adaptive Equalisation of Listen¬
ing Environment Acoustics, is likely to be¬
come as familiar as Dolby. Never heard of
it? Well, there’s lots more acronyms to
come, but eventually they will mean
something, particularly if we have some
hardware to do whatever the acronym
stands for.

Circuits for examining subcode are
starting to surface, and I suspect we are at
the edge of what could be the next area of
general interest for enthusiasts. Whether
we’ll all need degrees in digital audio is
another matter, but when you realise that
the Z80 is now nothing more than the 555
of the microprocessor world, it’s obvious
that we seem to be able to adapt to almost
any techological advance, even it takes a
little while.

Our first letter this month is about
CD digital audio, although it may raise
more questions than answers. However, it
shows what we may be in for, and I think
indicates that the time is coming when we
can get out of the armchair and take our

CD player into the workshop, where the
best entertainment is anyway...

CD subcodes

The following letter, by the author’s
description, is a ‘cut-down’ version of a
previous letter that was too long to include
in these columns. The letter briefly ex¬
plains CD subcodes, and ends with — no!
I won’t spoil the author’s surprise...

Most CD decoder or digital filter chips
now incorporate an output function known
as the 'Digital Audio’ or ‘Subcode Data’
output. The more upmarket machines have
an output socket on the rear of the player,
either in the form of an RCAlphono style
coaxial output or a 'Tosling' fibre-optic
transmitter port. The two outlets provide
the same information; the only difference
is the transmission method.

Either way, the signal is in the bi-phase
encoding pattern and runs at a clock
speed of2.8224MHz. The format is known
as SPDIF (Sony/Philips Digital audio
Interface), and is basically a subset of the
AESIIEC/EBU standard for digital audio
interfacing systems. The data in this serial
line alternately sends left and right audio
channel samples in 32-bit bursts; that is,
each 32-bit burst has 16 bits used for the
digital audio data. The other 16 bits are
used to tell the decoder certain statistical
details such as the sampling rate (32,44.1,
48kHz etc); whether it is audio data or
other data such as CDROM, CD-Interac¬
tive etc; if copying is permitted as per the
SCMS (serial copy management system)
used in DAT machines, two or four chan¬
nel audio, consumer or professional
source equipment; if de-emphasis needs to
be applied to the DAC circuitry; the
‘category code’ which states if the source
is from a CD, DAT, PCM adapter etc; a
CRC parity flag; the master clock ac¬
curacy; a ‘Data Valid flag; block and
frame sync bits; and a ‘U’ bit.

There are other bits as well, but the ex¬
planation of their use is long and detailed
and changes depending on whether the
source is domestic or professional gear.
The CD subcode system uses the U bit for
data transmission. The U bit is not defined
in the AES/EBUIIEC standard. It was
decided by Sony and Philips during the
development of the CD system, and the
subcode standard was published in the
much sought after Philips CD-DA ‘Red
Book’ standard, which is only available to
manufacturers.

The Subcode itself contains eight paral¬
lel data streams tagged P, Q, R, S, T, U, V
and W. Each channel is built up over time
to give a ‘subcode block’, such that each
of the channels forms a 98-bit word, which
is completely updated exactly 75 times a
second. So in each 32-bit word from the
decoder or filter chip, there is an audio
sample and subcode bit; that is, seven bits.

So, the sequence of transmission is Ql,
Rl, SI, Tl, Ul, VI, Wl, sync, Q2, R2, S2,
T2, U2, V2, W2, sync, and so on until Q96,
R96, S96, T96, U96, V96, W96. Then the
whole system wraps around and starts
again. Bits Q-W97 and Q-W98 are used as
frame sync bits. As there is only one U
channel bit sent in each 32 bit digital
audio word, during the time it takes to
construct a full block of subcode, there
are 1176 audio samples sent at a rate of
75 frames per second. This gives an
audio rate of1176 x75 = 88,200 left and
right samples per second, or a 44.1kHz
audio rate.

Only the Q bit is used in normal CD
players. The R-W bits aren’t used in stand¬
ard CD’s but this area is used to contain
the graphics information on discs encoded
in the CD+G (plus graphics) format. For
CD-I applications, all the subcode bits are
used, along with some of the audio bit sec¬
tors. One should note there is an unfor¬
tunate double usage of the terms P and Q

112

ELECTRONICS Australia, October 1992

channel in CD jargon. You must be careful
not to corf use the subcode P and Q chan¬
nel bits with the P and Q channel bits used
in the CIRC error detection-correction
system of the decoder chip. They are total¬
ly different bits.

The Q channel has several 1 modes of
operation . Of the 96 bits, several are used
for control, sync, CRC redundancy, pad¬
ding and address bits. The remainder are
used as 'active bytes to contain user data.
The way these are used depends on the
address mode code. Essentially, the active
bytes are used to convey any or all of the
following: track and index number, ab¬
solute time, relative time (in minutes,
seconds and frames), point and start time
of a track, lead-in or lead-out flags, bar¬
code catalog number of the disc, year of
recording, serial number, owner and
country codes and pause bits.

Although it would be possible to decode
this information with hard-wired logic
gates, it is more feasible to use a micro¬
processor. This way, alphanumeric titles
can be assigned to discs by having the
microprocessor recognise the unique bar¬
code number on any disc that is inserted
into the player.

The exact details of the way the subcode
data is decoded is a closely guarded
secret, held by the audio equipment
makers. However, by now you may have
guessed that I happen to have discovered
these details. The bad news is, Tm not
going to let on.

But the good news is Tm in the ad¬
vanced stages of designing an outboard
DAC unit for readers to construct for use
with CDs, DATs etc. The unit uses the very
latest in 1-bit DAC technology in a state-
of-the-art, class A configuration and will
have FULL subcoding information dis¬
played on the front panel including a few
fancy extras, such as CD+G decoder with
RF output. It will have multiple coaxial
and fibre-optic inputs, a headphone output
and infrared remote volume, as well as
automatic switching between 32,44.1 and
48kHz sample rates. It will also be avail¬
able for a fraction of the price of commer¬
cially sourced products. But you ll have to
wait a bit longer while the prototype un¬
dergoes full testing, before it hits the press.
(S.M., Townsville Qld).

I suppose most readers are rather like
me when it comes to CD players — they
are a unit that either works or not, and
that’s about it They can sometimes be
repaired if you have the manual but, more
often than not, you probably need align¬
ment jigs. In other words CD’s are a tech¬
nology that’s rather inaccessible, which is
something we electronic types are not en¬
tirely at home with.

Anything that allows us access to the

innermost workings of CD technology
is to be welcomed, so S.M., I for
one am certainly looking forward to
more details. And now back to more ar¬
cane matters.

NiCad discharger

The next letter asks a simple ques¬
tion; fortunately one that also has a simple
answer...

Using more and more NiCad batteries, I
am experiencing some trouble, such as
reversed cell polarity. I have therefore
decided to build the NiCad discharger
described in September 1989.

After purchasing all the components, I
sat down and read your article again to
get the full picture. However, nowhere in
the article do you explain why switch S2
has two positions for AA batteries.

There are even two different values of
discharge resistors for these two settings. I
would be grateful if you could please ex¬
plain? (GD., Burwood NSW).

When I designed the discharger, I pored
over suppliers’ catalogues and found that
there are two sizes of AA rechargeables:
500m Ah and 600m Ah. The most common
type seems to be the one rated at 600mAh,
but you just never know. Therefore, the
easiest way was to include both. This was
explained in more detail in the article
describing the companion charger.

And while we’re on the topic of
chargers...

Solar charger

The solar charger described in EA for
February, 1992 has been very popular
with constructors. Unfortunately, several
errors crept into the article, and these
were described as errata in the August
edition. However, not everyone has
caught up with the errata, including our
next correspondent:

I have recently purchased the solar
charger kit, described in February 1992.
In the layout diagram, component R2 is
not shown and the parts list and the circuit
diagram don't agree with the value of
some components. Also, I plan to use the
project to charge 12V batteries and I am
confused as to how the charger is con¬
nected to the solar panel. Could you
please help? (R.M., Mt Gambier SA).

First the errata. Resistor R2 is located
directly beneath C2, between C2 and IC1.
This resistor is 22 ohms, not 220 ohms as
shown on the circuit diagram. The other
incorrect value is Rl. This resistor is
shown as 180 ohms on the circuit and also
in the parts list Both are wrong — Rl
should be 180k.

Regarding your confusion about con¬
necting the charger to a solar panel, I must
admit to being unable to explain it any

differently to the article. The board is
simply connected to the solar panel as
shown in the layout diagram. That is, the
top wire in the diagram connects to the
positive output of the solar panel, and the
bottom wire connects to the negative out¬
put However, you might have some con¬
fusion about connecting the battery. A12V
battery is best connected with the positive
lead of the battery connected to the lead
marked ‘to battery +’ and the negative lead
to the common of the circuit This is the
same connection as the negative lead of
the solar cell.

Car wiring

Figuring out the wiring of a car trailer
plug can be quite a business, particularly if
there’s also a fault in the wiring. The next
letter describes a rather unusual testing
method that the author has used success¬
fully over the years:

To check caravan and trailer wiring, I
use a 12V, 100VA (or more) transformer.
To find the earth, clip one end to the frame
and touch out the plug contacts until a
good hefty spark identifies a short circuit.
Then using the known earth, identify each
pin using the acronym LISTER. That is
Left indicator, Interior light, Stop light,
Tail light, Earth and Right indicator. This
method blows no fuses and wastes no bat¬
tery power, although it can only be used
near a 240V power outlet. (R.M., Auck¬
land NZ).

An interesting method, R.M., and
probably more reliable than an ohmmeter
test Because it applies pretty much the
same test as the actual operating condi¬
tions, faults such as poor earth connec¬
tions, blown globes and so on are
quickly identified.

I’m familiar with the Utilux trailer plug,
which has earth as the centre pin. The
others are, to rearrange your acronym,
TLRS A, where A is an auxiliary circuit (or
interior light for a caravan). The pin num¬
bers are from 1 to 5, with 5 the auxiliary
circuit However, one never knows where
the wires might be connected, as ‘stand¬
ards’ always have their exceptions.

Scott connection

I’m glad the next correspondent took the
time to write, as I too had a few misgiv¬
ings about the answer to the What!! ques¬
tion posed in June.

The Scott connection, as explained in
July in answer to the June What?? ques¬
tion, is a means of connecting transormers
to give a 2-phase supply from a 3-phase
supply, and details are rather hard to find.
In fact, I analysed the reference material
given to me by the contributor of the ques¬
tion, and decided that the least said in the

ELECTRONICS Australia, October 1992

113

INFORMATION CENTRE

question (and the answer) the better. I’ll
explain later, but first the letter...

In response to the answer published in
July 1992 to the question from June, I
would like to make an observation. The
answer given is only partly right — con¬
necting two similar transformers as shown
will certainly provide the correct phase
relationship between the voltages for the
2-phase load, but not the correct voltage
levels for balanced loading.

I have drawn a diagram (see Fig.l)
using a phasor representation of the vol¬
tages, which is a technique often used
by electrical engineers (of which I am
one). In case they may be unfamiliar, let
me explain. They are like vectors, but
differ in that a vector representation of
alternating voltages would show a rotat¬
ing diagram.

In this stationary diagram, the phasors
show the inter-relationships of voltages
relative to a rotating datum. But the mag¬
nitude of the voltage is proportional to the
length of the line representing it, and its
phase angle relative to the common datum
is shown by its direction. In Fig.l, the
balanced 3-phase supply lines are desig¬
nated A, B and C.

The transformer connections are also
shown in Fig.l, in which you can see that
the centre-tap of transformer 1 is at a
potential midway between supply phases A
and C (because A and C are connected to
opposite ends of a single winding). But the
potential difference between this centre-

Fig.l

tap (X) and phase B is not equal to that
between A and C. In fact, taking mag¬
nitudes only: Vxb = Vad x 0.866.

It is clear from the geometry that the
phase relationship of the output voltages is
a right angle, which is correct for a
balanced 2-phase system, but the output
voltages are not of equal magnitude —
which they ought to be. With Vxb applied
to half the primary winding of transformer
2, its output voltage will be 1.732 times
greater than that of transformer 1. You
would obtain a voltage closer to the other
if the whole primary winding of trans¬
former 2 had been connected to Vxb, but
the two would still not be equal.

To obtain equal output voltages, the
standard Scott-connected transformers
have turns ratios differing by 0.866. That
is, for equal secondary turns, the primary
turns of transformer 2 should be 0.866
times the primary turns of transformer 1.

Thus, in the given conditions of the
problem, with two similar transformers
(taking that to mean that they have equal
turns ratios), there is no possibility of con¬
necting them to give a balanced 2-phase
output. Sorry about that! (K.M., Kangaroo
Ground Vic).

Don’t be sorry K.M. I agree with you.
When this question was given to me, the
text describing it included a phasor
diagram that I soon realised was impossib¬
ly wrong. I discussed this with a colleague,
and we both felt there should be a ratio of
0.866 somewhere in the system. However,
the text made no reference to this, so I
decided to present the answer as given in
the text, but in the hope that some discus¬
sion would arise. And fortunately it did.

In fact, another writer (P.M., Busselton
WA) makes the same point, so perhaps I
should say ‘sorry about that’ as my skill
with three-phase phasor diagrams died
some years ago and although I knew there
was something wrong, I wasn’t sure what
So thanks to both K.M. and P.M., for put¬
ting us all straight — I was waiting for
your letters!

Resistor network

As you can see from the last letter,
sometimes I have to take a punt when I
present the answer for a What?? question.
But at other times, I just plain ‘give up’
and pass it all over to you, folks. I used to
be red hot with resistor networks (I could
Thevenise and Nortonise along with the
best of ’em), but these days time is rather a
problem, and rather than solve the prob¬
lem asked by the next writer, I’m simply
going to present it:

/ first read this question some 30 years
ago. I have yet to hear of, or work out the
answer. Perhaps you can present it in your
column and maybe get me an answer.

The problem is: what is the resistance
between points A and B for the network of
one ohm resistors shown in Fig.2?
(R.V.H., Kallangur Qld).

So there it is everyone, all we need is the
answer. If I was able to offer a prize. I’d be
glad to give it to the first correct answer—
except I don’t know the correct answer!

However, I’m sure someone out there
can solve this problem, and the best I can
offer is the glory of having your name in
print And you’ll also have the gratitude of
our correspondent, who will have waited
over 30 years for the answer!

Car alarm

The next letter describes a problem in
our Car Burglar Alarm presented in
February 1991. It also gives a simple solu¬
tion to the problem...

After constructing the February 1991
car alarm, I found it worked perfectly on a
bench supply set to 13.8V. However ; it
would not latch on the delayed input when
connected to a 12V car battery (with a
terminal voltage of 12.6V). I checked
everything with a logic probe and it ap¬
peared OK up to C4. The warning light
was flashing quickly, indicating that the
main latch was operating and the clock
was changing frequency.

It appeared as though the alarm
latch was not receiving a sufficiently
strong pulse, although I had an indication
on a logic probe, suggesting something
was getting through. If I applied a pulse to
pin 3 ofIC3:A the alarm would operate, so
I checked the various components around
this part of the circuit, including C4.

I then changed C4 to a 220nF\ and
everything worked correctly. I have since
built a second alarm, and it displayed the
same fault. I don't understand why, but it
seems the value of C4 is too low. Apart
from this problem, the alarm is a great kit,
and I have a few people wanting me to
build them one. (RF., Warragul Vic).

Thanks PJF. for your kind remarks about
the project, and for sending this simple
solution to a problem that didn’t show up
during testing of the prototype. I think the

114

ELECTRONICS Australia, October 1992

reason is due to variations in the charac¬
teristics of IC3. Perhaps the IC used in the
prototype was more sensitive (as far as
triggering is concerned) than those you
have used.

Being an edge-triggered flipflop, if the
risetime of the pulse applied to the clock
terminal is not as sharp or as high as it
should be, unreliable triggering will
occur when the supply voltage is
reduced. Increasing the value of C4 is
the easiest solution, although it’s likely
the problem could also be solved by in¬
creasing the value of R5.

Radar detector

When I first read this letter, I thought
perhaps the writer had somehow missed
all the controversy that raged a few years
ago when radar detectors were declared
illegal. But not so, the question is about
radar detector detectors\

I have a question which I hope you can
answer, and which may be of interest to
other readers. Is it possible to detect the
presence or operation of a radar detector?

I have heard police advertising that they
have devices which can do just that, but I
am yet to be convinced that it can be done.
After all, a radar detector is supposedly a
passive device. What is there to detect?

If, as it seems to me, the authorities are
bluffing us, I wonder about the ethics of
such law enforcement methods. (B.R.,
CalwellACT).

Years ago I played around with radar
detectors. The unit concerned consisted of
a microwave antenna in the form of a spe¬
cially shaped rectangular aperture that
focused onto a microwave detector diode.

Thereafter, the modulation from the
detector diode was amplified by a conven¬
tional piece of audio circuitry. I recall that
the diode was the expensive bit, and I
think I destroyed it by doing something to
it I shouldn’t have done, like measuring its
resistance with an ohmmeter.

As the years progressed, radar detectors
became not only more popular, but smaller
and more reliable. But, as far as I know,
they all operated the same way. I am not
aware of any technology that can detect
the presence of what amounts to a
microwave tuned circuit, just as it’s not
possible to detect the presence of a radio
or a TV set by merely sensing its tuning
stage. Certainly, an operating TV set can
be detected by the RFI it produces, but a
radar detector as you say, is passive.

It may be that some types of radar detec¬
tors produce an output, and these are the
types being referred to by the police. Still,
if this is the case, it’s a rather blanket state¬
ment to suggest all types can be detected.
Although now rather academic, it’s an in¬

E B C

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Fig.3:

teresting question which someone might
be able to throw some light on.

Some might argue that the question of
ethics applies equally to those using a
radar detector, and those who claim they
can detect these devices. I should point
out that EA has always maintained that
radar detectors are unethical anyway,
and for this reason, we have never
described one as a project. Still, this
doesn’t preclude a technical discussion
about them. After all, they are illegal,
and if the police can somehow detect
them, then it shouldn’t worry any of us
honest citizens!

What??

It seems there’s an almost endless supp¬
ly of questions that involve resistors. TTiis
month’s question comes from Graham
Lead beater, of Ringwood in Victoria.
Graham asks:

Using only perfect one ohm resistors,
construct a network that gives a total
resistance of pi ohms, correct to six
decimal places. That is, 3.141592654
ohms. What is the minimum number of
resistors required?

Answer to

September’s What??

A possible solution is shown in Fig.3.
For no switches operated (as shown), the
terminals to the transistor under test are
EBC. With SW1 operated, they become
ECB, with SW2, CBE and BEC for SW3.
If both SW1 and 2 are operated you get
BCE, with CEB for SW1 and SW3.

There are other possible switch com¬
binations (SW2 and 3 or SW1, 2 and 3),
but these only duplicate some of the per¬
mutations already listed. ♦>

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ELECTRONICS Australia, October 1992

115

READER INFO NO. 12

SHORTWAVE

LISTENING

by Arthur Cushen, MBE

New countries and new voices on air

International broadcasting is expanding, and Costa Rica and Hawaii are about to join the countries
with international services. Also, many of the Republics of the former Soviet Union are now
operating their own services, such as Radio Ukraine International. The exchange of facilities also
continues, with Radio Japan's broadcasts now being relayed by the BBC.

The Spanish Foreign Radio in Madrid
has constructed transmitters in Costa
Rica, to carry programmes into the Carib¬
bean and South America. There will be
three lOOkW transmitters in service and
all broadcasts will be in Spanish. There
has been some delay in getting the trans¬
mitters operational, according to Radio
Nederland, but by the time this is publish¬
ed, the three transmitters should be in ser¬
vice. The transmitters will operate from
2200 - 0500, and will carry the best of
the Spanish World Service, linked by
satellite from Madrid.

116 ELECTRONICS Australia, October 1992

The frequencies are yet to be decided,
but it is expected that the tropical
band, 60 metres, will be used, along
with frequencies in the six, nine and
11MHz bands.

New voice from Hawaii

A second international voice from
Hawaii is planned to be in operation by
December 1993. Hawaii's first shortwave
operation was that of the Voice of
America, which I first heard at 0900
on 15 May 1947 — they were using
lOOkW on 15,250kHz. For the following

several years, KRHO, the call of the Voice
of America station, was heard on an addi¬
tional six frequencies, until it was taken
out of service in the late 1950s.

The newcomer to shortwave from
Hawaii will be KWHR. The owners are
WHRI, operated by the LeSea Broad¬
casting Corporation from South Bend,
Indiana.

KWHR will be built on the big is¬
land of Hawaii, and will be able to
reach a large part of Asia, the Central
Pacific and Australia. The transmitter will
probably be a Harris lOOkW similar to
the ones being used by WHRI. With its
slewable curtain antenna, it should cover
from Sydney to North of Tokyo. Program¬
mes will be fed from WHRI, in Indiana by
satellite. In the call of the new station, 'K'
is the call for stations west of the Missis¬
sippi and then W stands for World, 'H'
for Harvest and 'R' for radio.

The goal of WHRI, which already owns
a television station in Hawaii, is to be on
air by December 1993. Its curtain array
will operate on nine to 18MHz, but due
to propagation problems during daylight
hours, a smaller antenna will be used for
the Pacific broadcast

Japan using BBC relay

Radio Japan is using the facilities of the
BBC transmitter at Skelton in the United
Kingdom, to broadcast into the Middle
East, Europe and Africa. Following a
series of test broadcasts, the relay is now
in regular operation. Transmissions are on
9670 and 9695kHz, 0400 - 0800UTC
and on 9770kHz, 0400 - 0600. Broad¬
casts in English are heard between 0500 -
0600 and 0700 - 0800. Other transmis¬
sions in English are 2100 - 2200 on
11,735kHz and 2300 - 2400 on 6025 and
6160kHz.

Radio Japan is interested in the recep¬
tion of its new BBC relay, and is request¬
ing reception reports to Radio Japan/NHK
Tokyo, 150-01, Japan.

Shown here are people in Ceel Buur in central Somalia, as they tune into the BBC
Somali Service's reports about fighting in Mogadishu. The Missing Persons'
programme also has a large listening audience. (Photo credit Hamish Wilson.)

Rumania, Yugoslavia and Italy. This quick
expansion for AWR has brought along
with it some tough new challenges.

New studios and equipment are being
organised, personnel are being recruited
and trained, and the programme distribu¬
tion system is being streamlined.

English is broadcast on 0430 - 0500 on
15,125kHz; 0600 - 0630 on 11,775kHz,
and 1600- 1630 on 15,125kHz.

ELWA returns to shortwave

During 1990, the Civil War in Mon¬
rovia resulted in the giant complex of
VOA being completely destroyed — the

AROUND THE WORLD

ALASKA: KNLS Anchor Point has announced its schedule which is valid to March
27, 1993. English is broadcast at 0800 - 0900 on 7365kHz, and 1300 - 1400 on
11,580kHz, but from September 27 this will be changed to 7355kHz. Other lan¬
guages up to September 26 are: Russian 0900 - 1000 on 11,820kHz; Mandarin
1000 - 1200 on 9600kHz; Russian 1200 - 1300 on 7365kHz and 1600 - 1800 on
9615kHz. From September 27, broadcasts up to 1300 will be on 7365kHz, up to 1700
on 7366kHz, then to 1800 on 6150kHz.

AUSTRALIA: Radio Australia is testing on the very high frequency of 25,750kHz at 0800
- 0900 daily. The tests are from the Darwin 250kW transmitter and are being sent on a
polar path so that scientific investigations can be carried out on the performance of the
signal. Radio Australia's 'Communicator', a programme on the latest developments in
the media and communications world, is heard on Tuesday at 0930 and repeated at
1130, with the best reception being on 9580kHz for both transmissions. At 1130
transmissions are also heard on 6080, 7240 and 9710kHz.

BOLIVIA: Radio Fides from La Paz carries a transmission of request music in Spanish up to
0600 on Sunday. The frequency of 4845kHz has been received with the alternate channel
of 6155kHz providing fair preception.

BOTSWANA: The Voice of America is operating four lOOkW transmitters, and these
have been heard from 0400 - 0700 carrying English programmes, some at very
good strength. At 0500, 9885 and 15,600kHz are the best channels received. Ear¬
lier at 0400 - 0500, the English Service is on four frequencies: 7265, 7280, 9885
and 11,940kHz, but only 9885kHz is audible in this area. A special verification
card is being issued for VOA Botswana, and reports should go to the Voice of
America, Washington DC 20547, USA.

GUATEMALA: Station TGNA, a gospel broadcaster with the call sign standing for Tell¬
ing Good News Abroad' is heard on 3300kHz with English up to 0430. This is audible
mainly in the winter months, but there is an alternative broadcast available at 1100 in a
local language.

NEW ZEALAND: Print Disabled Radio, Levin ZLXA is now being widely received in the
South Pacific on two frequencies. The normal evening broadcast is at 0600 - 1000
Monday to Friday, on 3935kHz using IkW. ZLXA's new frequency is 7290kHz, operat¬
ing Sunday to Thursday from 2200 through to 0600 the next day. Despite its small 250
watts of power, it has been reported from Australia in its initial test. Reports are re¬
quested, along with return postage, to ZLXA, PO Box 360, Levin.

TONGA: The Tonga Broadcasting Commission's transmitters were struck by a hurricane late
last year and put out of service. Its mediumwave outlet of 1017kHz was soon back in
operation, but the shortwave transmitter on 5030kHz was in a different building which was
severely damaged.

Early plans were announced to move the shortwave transmitter of 1 kW to the mediumwave
building and this has been accomplished. However, it has now been found that the trans¬
mitter has some faults. It is not on the air at the time of preparing this material, but when it
returns, it should be heard closing at 1000. There have been reports from North America of
reception of Tonga on 5030kHz but it is obvious that the listener is tuned to the Solomon
Islands on 5020kHz.

UKRAINE Radio Ukraine International, Kiev, has English to Europe and North America
0000 - 0100 on many frequencies, with 12,040 and 12,060kHz giving the best recep¬
tion. The station, previously known as Radio Kiev, is requesting reception reports on
these transmissions.

UZBEKISTAN: Radio Tashkent has a new morning service to Asia which is giving good
reception in the South Pacific. The broadcast in English is at 0100 - 0130 on 7235,
7325, 9740 and 11,975kHz, with the last channel giving the best reception.

Russian AWR transmitters

Recently Adventists World Radio began
broadcasting to Europe over Radio Mos¬
cow facilities. The broadcasts are coor¬
dinated in a studio near the edge of Red
Square in Moscow.

AWR is using three different transmit¬
ters for these new broadcasts. A
250kW transmitter at Samara reaches into
Scandinavia and Northern Europe; from
Ekaterinburg a 200kW transmitter targets
the countries of Germany, Poland and
Czechoslovakis; and a 250kW transmitter
located in Moscow will broadcast to

same fate suffered by ELWA, the well-
known gospel broadcaster. The Voice of
America has remedied the situation some¬
what by opening four 10OkW transmitters
in Botswana, while ELWA is back in Mon¬
rovia and is operating on FM.

ELWA has been quick to return to the
devastated city and its FM broadcasts
are operating 20 hours a day, giving
good local coverage.

When the staff returned, they found
that nearly all the facilities were
destroyed; studios were levelled, trans¬
mitters demolished and generators
smashed. The only salvageable items
were a few antenna.

Its plans for the future include the
installation of two lOkW shortwave trans¬
mitters which will enable ELWA to again
reach the 25 West African language
groups it served in the past.

It will be received worldwide by
shortwave listeners, as it has been over
the past 37 years of operation. ELWA
did not miss a day's broadcasting ex¬
cept for the Civil War, and was back in
operation in January 1992 after 18
months of silence.

BBC Somali service

In war-torn Somalia where there is
chaos, famine and no Government, the
main source of local news for the popula¬
tion is the BBC Somali Service.

Interesting items from one of the
refugee camps in Ethipia indicate that the
keenness to listen is such that one Somali
exchanged his food ration for some bat¬
teries so he could tune in the BBC.

In a country starved of food, shelter and
health care, the BBC brings information,
education and entertainment in the lan¬
guage of the people. Its Missing Persons
programme, on the air six days a week,
provides a vital link for families torn apart
by war and famine.

The broadcasts in Somali commenced
in 1957, and are now broadcast one hour
a day. The Somali Broadcasting Service is
listed as broadcasting on mediumwave
from Mogadishu using 962kHz with
150kW, and on shortwave 7200kHz with
a schedule 0300 - 0500, 0900 - 1200 and
1500-1900.

It is interesting to note that Radio On-
durman in the Sudan is also using
7200kHz, and has been received at 1745
when testing its 10OkW transmitter. ❖

This item was contributed by Arthur
Cushen, 212 Earn St. Invercargill,
New Zealand who would be pleased
to supply additional information on
medium and shortwave listening. All
times are quoted in UTC (GMT)
which is 10 hours behind Australian
Eastern Standard Time.

ELECTRONICS Australia, October 1992

117

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sizer or sampler. If you want to go beyond
using the factory presets or the random poking
of buttons, then this is the book for you.
CODE: PC 1003 PRICE: $18.95

Computers and Music - An Introduction:

This book explains how to simply set up your
own computer music studio. It covers the basics
of computing, running applications programs,
wiring up a MIDI system plus everything about
hardware and the programs.

CODE: PC 1006 PRICE: $23.95

Practical
Electronic Filters

Practical Electronic Filters

Practical Electronic Filters explains in a simple
form, the understanding of how to work a fil¬
ter. It presents projects to apply in and around
the home, including diagrams that are suited to
the beginner and a more advanced constructor.
CODE: BP 2990 PRICE: $13.00

How to set up a

HOME RECORDING
STUDIO

DAVID MEUOR

How to set up a home Recording Studio

If you have a studio at home or are about to
set one up, this book is for you! It describes
the setting up of an 8 to 16 track studio with
an outline of the musical and recording gear
needed.

CODE: PC 1009 PRICE: $21.95

Electronics - Build and Learn

This book is the perfect balance of theory &
practice. It introduces common electronic com¬
ponents and how they are built into useful cir¬
cuits. An essential for the beginner, providing
practical tests and experiments.

CODE: PC 1008 PRICE: $18.95

AReferenceGuideto
Basic Electronics
Terms

A Reference guide to Bask Electronk Terms

A comprehensive A to Z guide of electronic
terms. This book chooses and explains some of
the more important fundamental terms (over
700), making the explanations easy to under¬
stand and avoiding high level mathematics.
CODE: BP 2860 PRICE: $16.00

electronics

DATA

BOOK

Mike Toolev BA

Everyday Electronics Data Book

This book is an invaluable source of informa¬
tion of everyday relevance in the world of elec¬
tronics. A must for everyone involved on elec¬
tronics who wants to put theory into practice.

CODE: PC 1012 PRICE: $26.95

Electronk Projects for Home Security

This book deals with the many aspects of
home-security and how to construct your own
security system. It covers the latest in technol¬
ogy, whilst remaining simple and reliable in its
instruction.

CODE: PC 1010 PRICE: $21.95

ELECTRONIC
POWER SUPPUT

Jfyndtrt ok

IAN R SINCLAIR

Electronic Power Supply Handbook

This book covers the topic of electronic power
supplies, including batteries, simple AC sup¬
plies, switch-mode supplies and inverters.
Subjects dealt in detail are devices, their oper¬
ating principles and typical circuits.
CODE: PC 1001 PRICE: $23.95

Mini Matrix Board Projects

This book provides you with 20 useful and
interesting circuits, all of which can be used on
a mini matrix board, which is just 24 holes by
10 copper strips.

CODE: BP 9900 PRICE: $6.50

Coil Design and

Construction

Manual

B. 8 BABA.NI

Coil Design and Construction Manual

A unique book for both the professional and
home constructor on 'How to Make' your own
R.F., I.F., Audio and Power coils, chokes and
transformers etc.

CODE: BP 1600 PRICE: $6.50

DIGITAL
LOGIC GATES
AND FLIP-FLOPS

H/hat-fatydo find hnv tv t*fc av*n

Ian R Sinclair

Digital Logk Gates and Flip-Flop

Intended for enthusiasts, this book aims to pro¬
vide a firm understanding of gates and flip-
flops thoroughly and from the beginning. It is
for the user who wants to know more than a
few rules of thumb about digital circuits.
CODE: PC 1013 PRICE: $26.95

The PC Music Handbook

This book takes the reader through the cre¬
ative possibilities of the personal computer.
Full of practical tips on equipment plus expla¬
nation of sequencing, sampling and notation.

CODE: PC 1005 PRICE: $28.95

HOW TO ORDER

To order, simply fill in the coupon, remembering to
include the code numbers and $5.00 postage and
handling. If the coupon is missing, write down the
names, code numbers and prices of the books you
require. Include your name, address, phone number,
plus cheque, money order or credit card details (card
type, card number, expiry date and signature) and
send it all to Federal Publishing, Reply Paid No. 3,
PO Box 199, Alexandria, NSW 2015. Please allow
at least 28 days for delivery and please sign all
orders.

50and25 years ago...

'Electronics Australia' is one of the longest running technical publications in
the world. We started as 'Wireless Weekly' in August 1922 and became 'Radio
and Hobbies in Australia' in April 1939. The title was changed to 'Radio,
Television and Hobbies' in February 1955 and finally, to 'Electronics
Australia' in April 1965. Below we feature some items from past issues.

October 1942

Radio licences: The latest return of
broadcast listeners’ licences shows that
South Australia has 22.51 licensed radio
receivers to 100 people.

Western Australia is next with 19.73,
Tasmania has 19.56 and Victoria 19.14.
New South Wales has a percentage of
only 17.94.

The total number of licensed sets
throughout the Commonwealth at July
31st last was 1,330,619, an increase of
10,546. Half this increase resulted from
new provisions requiring operators of
more than one radio receiver to obtain a
supplementary licence.

Picturegram service suspended: The
picturegram service, by means of which
facsimiles of photographs, prints and all
kinds of documents may be transmitted
telegraphically between Melbourne and

Sydney is to be suspended for the dura¬
tion of the war.

The facility has been in operation
nearly 14 years, and the maintenance of
the service under present conditions rep¬
resents a serious problem to the depart¬
ments because of the difficulty of
securing replacement parts.

October 1967

Microcircuits: Nowadays, just about
every news-sheet and technical journal
related to electronics is heavy with ar¬
ticles on microcircuits, integrated cir¬
cuits or ICs — call them what you will.
To copywriters they are ‘new and
exciting’, but I suspect that a good many
technically involved people — and cer¬
tainly hobbyists — basically resent their
appearance. Transistors took some get¬
ting used to, but they were distinct com¬

ponents, large enough to be handled and
capable of being incorporated in¬
dividually into design.

But ICs, with their circuitry con¬
centrated onto a single microscopic chip,
make the best efforts of circuit designers
to date look unspeakably clumsy by
comparison.

Like it or not, microcircuits are des¬
tined to dominate electronics. We may
as well move over now!

Seismic centre in Sydney: A $lm
seismic data processing centre has been
opened in Sydney by Texas Instruments
to speed oil search and other geophysi¬
cal work in Australia.

It will provide the first advanced seis¬
mic services in Australia Previously, all
data requiring extensive processing had
to be shipped out of Australia.

The computer, called a digital seismic
data processing unit, eliminates much of
the cluttered information contained in
seismic data. It does this at high speed
and produces a chart which depicts the
significant contours of subterranean
areas more clearly than has previously
been possible. The use of Texas
Instruments’ technique in Canada had
pinpointed oil-producing structures so
accurately that about 80% of wells
drilled produced oil. ❖

EA CROSSWORD

ACROSS

1. Central part of IBM. (8)

5. Colloquial term for
telephone. (6)

10. That which denotes a
number. (7)

11. Coupling device. (7)

12. A form of capacitor
structure. (4)

13. Aims sensor or beam across
a surface. (5)

14. Type of rectification,

-wave. (4)

SOLUTION
FOR SEPTEMBER

17. Subject to analysis. (5)

18. Titanium ore. (6)

21. French scientist, Blaise-,

noted for hydrodynamics
law. (6)

22. Repetitive parts of computer
program. (5)

26. The-switch is mercury

based.(4)

27. Operational problem. (5)

28. Selenography is the study

of the-.(4)

31. Silhouette of a circuit, etc. (7)

32. Items that lift and separate. (7)

33. Type of antenna. (6)

34. The last word in IBM's
expansion. (8)

DOWN

1. Said of two-digit notation. (6)

2. Measures values of
variables. (7)

3. Accepted average standard. (4)

4. Join tape, etc. (6)

6. Metal used in solder. (4)

7. Power rating. (7)

8. Said of space in Geissler
tube. (8)

9. Metallic element number 72. (7)

15. Word in logic table. (5) _

16. Said of one of an ellipse's
axes. (5)

19. Country of origin of Alexander
Bell and James Maxwell. 8)

20. Add-in vocal system. (7)

21. New name for handheld
computer. (7)

23. Communication from public

to radio station. (5-2)

24. Ionised gas. (6)

25. Well-known brand of
computer. (6)

29. American gospel music with
blues blend. (4)

30. Composer of keyboard (or

clavier) music. (4) _

120

ELECTRONICS Australia, October 1992

EA with ETI marketplace

ADVERTISING RATES FOR THIS PAGE

SMALL ADS: The minimum acceptable size of 2 centimetres x one column costs only $50. Other sizes up to a maximum of 10 centimetres are
rated at $30 a centimetre. CLASSIFIEDS: $4 for 40 letters. Just count the letters divide by 40 and multiply by $4, ROUND UP TO THE
NEAREST WHOLE NUMBER. CLOSING DATE: Ads may be accepted up to the tenth of the month two months prior to issue date. PAYMENT:
Please enclose payment with your advertisement. Adress your letter to: THE ADVERTISING PRODUCTION MANAGER, ELECTRONICS
AUSTRALIA, P.O. BOX 199, ALEXANDRIA NSW 2015 FAX: (02) 693 9997

FOR SALE

T.V.YOKE EXCHANGE

Prompt service.

Refer transformer rewinds this page.

Phone (065) 761 291
Fax (065)761 003

UNUSUAL BOOKS: Fireworks,

Locksmithing, Radar Invisibility, Surveillance,
Unusual Chemistry and More. Send SASE for
catalogue to : Vector Press, Dept E, PO Box
434 Brighton SA 5048.

WEATHER FAX PROGRAMS: For IBM

XT/AT’s *** “RADFAX2” $35, is a high
resolution, shortwave weather fax, morse
& RTTY receiving program. Suitable for
CGA, EGA, VGA & Hercules cards (state
which). Needs SSBhf radio & RADFAX
decoder. *** “SATFAX” $45, is a NOAA,
Meteor & GMS weather satellite picture
receiving program. Needs EGA or VGA, &
“WEATHER FAX" PC card. *** “MAXISAT”
$75 is similar to SATFAX but needs 2mb
of expanded memory (EMS 3.6 or 4.0) &
1024 x 768 SVGA card. All programs are
on 5.25” or 3.5” disks (state which) +
documentation, add $3 postage. ONLY
from M. Delahunty, 42 Villiers St, New
Farm 4005, Old.

Ph (07) 358 2785.

MY AUSTRALIAN DESIGNED: Low cost
super fast Z80 micro-controller
development system has gained
acceptance already with educational
institutions. Pop it on the end of any PC
MSDOS or Z80 machine and away you
go. Boards, EPROM, and 720K disk $76
including postage for a short form kit. Gee,
I wish I had this when I was a kid. For
more info, send a 45c stamp to Don
McKenzie 29 Ellesmere Cres Tullamarine
3043.

FIX-A-KIT

KIT REPAIR AND CONSTRUCTION
3 months warranty on repairs
12 months warranty on construction,
technical assistance.

HYCAL ELECTRONICS

Design, Manufacture, repair of electronic equipment

(02) 633 5477

SELL OLD RADIOS: Valves, Keys,
Transformers, Books 07 356 6052.

OVER 4000 PRINTER BUFFER KITS:

sold from home since Jan 85. A 4Mb
SIMM/SI PP version can be built with only
7 additional common chips. Z80 based.
Speeds from 4 to lOMhz. Short form kit
$52. For more Info send 45c stamp to
Don Mckenzie 29 Ellesmere Cres
Tullamarine 3043.

AMIDON FERROMAGNETIC CORES:

For all RF applications. Send business size
SASE for data/price to RJ & US IMPORTS,
BOX 431 KIAMA NSW 2533. Agencies at
Geoff Wood Electronics, Sydne: Webb
Electronics, Albury: Assoc TV Service,
Hobbart:: Truscott Electronics, Melbourne.

8051 MICRO-COMPUTER
/PROTOTYPING PCB $30: Similar to my
ROMLoader EA Jan 92. Provisions for
8255 PPI.9346 EEPROM, 2k - 32k
SRAM, 2k - 32k EPROM, MAX232, DIP
switches & expansion header. Send A4
SAE for article. Tantau PO Box 206
Gordon 2072.

CIRCUIT SIMULATION

Learn it the friendly way with the best

student software

Micro-Cap III analog.$65

Micro-Logic II digital.$65

and top books by respected authors:
Electronic design,

circuit and systems.$46

Digital Microelectronics.$46

All post free in Australia

p.s We support our student customers!
Call David on (02) 639 3507
David Spalding Pty Ltd
458 Blackett Dr. Castle Hill NSW 2154

TRANSFORMER REWINDS
ALL TYPES OF TRANSFORMER REWINDS

TRANSFORMER REWINDS

Reply Paid No.2, PO Box 438 Singleton, NSW
2330. Ph: (065) 76 1291, Fax: (065) 76 1003

DESIGN & DEVELOPMENT

The “ONE OFF ” Specialists
DALEY ELECTRONICS PTY. LTD.
ACN 005 279 809

84 Keys Rd Moorabbin (03) 555 5153

SIMPLE IBM PC DATA ACQUISITION
AND CONTROL: C001 -Plans and
software for a one chip, 8 channel analog
to digital converter that plugs into the
printer port. Suitable for laptops or
desktop-$25.00 -C002-A small, 15 degree
per step, unipolar, stepper motor plus
plans for a one chip printer port interface
and software source code showing how to
drive the motor in wave, full step and half
step modes-$25.00»C003- Plans and
software for a remote four button keypad.
Uses the serial port, no external power
required-$25.00. All prices include post
and packing within Australia. To order
send cheque or money order to lambda
systems PO Box 259 Unanderra NSW
2526 or send SSAE for more info.

WANTED

OLD MICROPHONES FOR COLLECTOR:

Ribbons, Carbons, Condenser from
Broadcast and PA.

John Henderson 09 279 1234

LEGIBLE COPY: Audio 1C OP AMP
Applications, by W.G.Jung, pref 3rd ed.,
Pub. Howard Sams. Will pay new price
or neg. Offers please: PO Box 65 Hall,
ACT, 2618. (06) 230 2429

TRAEGER SSB 100: Channel kit for
2MHz, preferably 2020KHz or complete
transceiver if price is right. Contact Nic
Mclean (08) 261 3977
Fax (08) 266 3477

j RAim)Pr> Ltd j

Established 1933
IS THE ONLY COMPANY WHICH
MANUFACTURES & SELLS EVERY PCB
& FRONT PANEL
published in EA & Silicon Chip.

651 Forest Road. Bexley 2207
AUSTRALIA

RING (02) 587 3491 FOR INSTANT PRICES.

KIT REPAIRS

Kits repaired from all magazines.
Switchmode power supplies repaired.
Design work from start to finish.
Computer software consultancy.

Ring anytime 9am-9pm Mon-Sun

EEM Electronics

10 Bouverie Place, Epping Vic 3076

(03)401 1393 _

m!iMimm P iiM IT,p For lisl 01 9tl ’ e1 ' ltlclulHl1 ? y,lYtt * tewl Posla9e 81311111 Fwi lisl .° l ileins lnc!udll1 G Va!ves * 881111 Postage Stamp For List'01 Other Items Indudag Valve:»tod Postage Stamp For list in OHiep items Including Valves

Send Postage Stamp For List Of Other Items Including Valves

L.E. CHAPMAN

SUPER SPECIAL

FM Stereo Kits with circuit diagram

All three modules supplied are fully
assembled and aligned only $22 pp
$280

Tuning Capacitor

2 gang covers all
Aust. AM bands
$4.75 pp $150 for ^
One or two

Tape deck or radio power leads, plug

and sockets $150

Test prods and leads $1.50

Touch micro switches as used on colour
TV sets 4 for $1

Transistor ear pieces plug & lead 4 for $2
Push button switches 4 pos 50c

Speaker Transformers

7000 to 15/OHM 5W $7
7000 to 3.5 OHM 15W $10
5000 to 3.5 OHM $7
SPEAKERS 5- 8 Watt $6 15/Ohm,
5* 715/Ohm $7.6x 4 15/Ohm $7.

Electros 20uF 450V $1.50
IOOuF 350V $2. 2000uF 25V

Inline fuse holders 4 for $1
Shielded leads 7ft 35 to 35 $1
35 to 65 $1
65 to 7 ft 75c
Inline Bay not Plugs
$ Sockets 4 for $1

Shielded Cable 20 cents a metre

Tag Strips 10 for $1.00 Mixed

Two Way Speaker Crossover
Network $2

Capacitors

6N8150V
IOOOuF16V
IOOOuF 50V
0 0039uF1500V
0 0068 250V
47uF63V
47uF160V
470uF16V
47uF 200V
0.1 uF 250V
680uF 40V
0.027 250V
IOuF 25V
22uF160V
0039mfd 400V

50c
50c
$1 ea
50c
10 for$1
$1 ea
3 for $1
3 for SI
$1 ea
5 for $1

3 for SI

4 for $1
10 for SI

5 for SI
4 for $1

1c Sockets

18 pin • 24 pin • 28 pm
All 4 for SI

R.C.A plugs and sockets 50c
pair

2.5mm sockets 4 for SI

3.5mm sockets 4 for $1

6.5mm sockets 4 for $1

Thermisters 4 for $1

Speaker plugs & Sockets
4 pin 50c pair

2 pin 50c pair

POTS

Vi MEG $1.50 Dual 2 MEG Ganged
Lin $2

Vi MEG Switch $2 Dual 1 MEG
Ganged Lm $2

1 MEG $150 Dual 1 MEG Ganged
Log $2

1 MEG Switch $2 Dual 10K Ganged
Log$1

25K Dual Ganged $2 50 OHM Single

50c

Slide Pots

Vi MEG Dual $1 2SK Dual S2

1 MEG Dual $2 5K Single 50c

2 MEG Dual $2 250K Single 50c

IK Dual $1 10K Single 50c

5 Mixed Rotary Switches

5 for $250 Special

Special

12 Mixed Switches $450

200 mixed screws self-tappers bolts,
nuts. etc. 200 for $2

Car Radio Suppressors

4 for $2

Valve Sockets 9 Pin 4 for $2
Octal 4 for $2

Stick Rectifiers TV20SC $2
Transistors AD 161-162 pair $3 AD
149 $2 each

TV CRYSTALS

4433/619 $2 00
88/238 $2 00

Microswitches SA 250V AC 50c

Chrome ’A push on knobs RRP
S1.20 ea 10 for SI

Mixed Capacitors fresh stock 100 for

Mixed Resistors all handy values

100 for S2

Slide pot Knobs 10 for $1

IFS 455K for Valve radios $2 ea

Oscillator Coils $1 ea

Dynamic Microphone Desk type HI

IMD on/off switch $4 ppSl

Tersco Microphone Ceramic S2 pp

fbM

SUPER SPECIALS
MULTICELLULAR
HORN TWEETER
8ohm, 30 Watt
Crossover 3KHz
Frequency
2,000/20.000 105db

Shielded Cable Audio Leads 7 ft
with plugs 6.5 to 35
3.5 to 3.5 SI each

TRANSFORMERS 240V to 63
$9 each 240to9V

Valves

6K7 S10EF50 $5 6J5 $10

EF80 $10 6K8 $10 6CQ8 $10
6V4 $6 1S5 $7 6CM6 $10

6AL3 $6 6BM8$8 6CM5 $10

68L8 $5 5AS4 $10 6AU6 $10
6U7 $10 IT4 $7 6AS6 $10

6SA7 $10 6V6 $10 6AN8 S10
12AX7 $10 6L6 $15 6136 $10
6805 $10 6AM8 $10 6005 $10
6AV6 $8 6SL7 $10 12AU7 $10
6SN7 $10 205A $10 12DL8 $10
12AT7 $10

122 PITT ROAD,
NORTH CURLCURL,
NSW 2099.

PHONE (02) 905 1848

Send Postuge Staug Fur List tH Otter Hem s Including Valves

Amateur
Radio New§

35th JOTA this month

The 35th annual Jamboree- on the
Air (JOTA) is being held this month,
on 17-18 October, and is expected to
involve some 400,000 scouts and guides
around the world.

In Australia about 40,000 boys and
girls are to take part in this interna¬
tional activity, thanks to the co-operation
of radio amateurs and electronics/com¬
puter enthusiasts. JOTA is the high point
in the radio scouting calendar, and some
160 JOTA stations are planned to be
operating in NSW alone.

The importance of JOTA has been
recognised by the World Federation of
Great Towers (WFGT), which is staging
its Children’s WorldCom Day on Oc¬
tober 17 to associate it with the Jam¬
boree. Included in the 17 towers taking
part in the WFGT event will be the Syd¬
ney Centrepoint Tower and the Telecom
Tower in Canberra.

The Centrepoint Tower operation is
being staged by the Bankstown
Amateur Radio Club, in conjunction
with the Central Sydney area of the
Scout Association.

WA holding ‘Hamfest 92’

Alex Petkovic VK6APK, of the
Northern Corridor Radio Group in
Western Australia, has advised that the
Group will be staging ‘Hamfest 92’ on
Sunday November 1st. This year’s
event is expected to be the largest yet
seen in WA, and as in previous years
entry will be free.

Further details are available from the
NCRG by contacting the Group’s station
VK6ANC, or by mail to PO Box 244,
North Beach 6020.

Going overseas?

Want to be recognised as an amateur
wherever you go? The WIA’s Federal
Office has on hand stocks of the
Institute’s badge, in the internationally
recognised diamond shape. There are
two versions, the standard diamond
badge, and one with space to have your
own callsign engraved.

Both versions can be obtained through
the WIA’s Divisional Bookshops for
$4.00 each. If not in stock already, the
Bookshop Officers will be happy to get
them in for you.

New radio club
in NE Adelaide

The North East Radio Club (NERC) is
a relatively new group operating in the
north-eastern suburb (Tea Tree Gully)
area of Adelaide. It is affiliated with the
WIA, and has established a club station
with the callsign VK5GRC.

Goals of the club are to bring together
people with a common interest in
electronics and radio communication,
and to increase public awareness of the
role of licensed radio amateurs.

Membership is open to people of all
ages, with the common interest — rang¬
ing from junior experimenters, through
scanner and shortwave listeners, CB
radio operators and radio amateurs.

Club activities include training, tech¬
nical assistance, lectures, field days and
running a technical reference library.

Club president is Peter VK5ZFW,
with Rob VK5KP as chairman of the
membership committee.

Further information is available from
the North East Radio Club Inc., PO Box
568, North Adelaide 5006.

Morse exams

The WIA Exam Service reports that
some candidates are failing simply from
nerves, rather than from lack of ability to
receive Morse code.

One of the main hopes of the devolved
system was that in smaller groups
and in familiar surroundings, can¬
didates would be more relaxed and so
able to perform better.

Most examiners go out of their way to
make conditions comfortable for can¬
didates, some of them playing the prac¬
tice section two or three times to help
settle the nerves before the actual test is
run. Others have taken considerable
trouble to ensure the best possible
quality reproduction of the tapes.

The Exam Service sends its thanks to
those who have made so much effort for
the sake of amateur radio’s new recruits.

It also sends a word of advice to
those candidates who are practising
sending Morse code by automatic
means: the regulations say that the
candidate must demonstrate the ability
to send ‘by hand’, so go back to the old
key and practise on it, before you at¬
tempt the examination! ♦>

READER INFO NO. 23

Professional

Electronics

♦ ♦♦ ♦ ♦ ♦ ♦ ♦♦

REVIEW OF DADiSP 3.0:
DATA ANALYSIS/DISPLAY
PACKAGE FOR PC'S

TEST & MEASURING
INSTRUMENTS FEATURE

RF SIGNAL GENERATORS:
KEY PARAMETERS

NEWS HIGHLIGHTS

CSIRO DEVELOPS MULTI-
BEAM SATELLITE ANTENNA

Until now, one of the limits to the
growth of communications and broad¬
casting via satellites has been the cost of
antennas — in terms of both money and
‘real estate’.

Parabolic dish antennas must
generally be used, in order to achieve
sufficient gain, and conventional
designs have sufficiently narrow beam
widths that a separate dish must be used
for communication with each satellite.

However this has now changed.
Australia’s CSIRO Division of
Radiophysics, with support from the
Department of Defence, has developed
a novel multi-beam antenna which
provides a cost-effective way to access
more than one satellite using a single
antenna.

A development from the traditional
Cassegrain system, the new antenna uses
an offset secondary reflector and special
shaping of the reflectors to allow them to
be used by multiple feedhoms. For a par¬
ticular orientation of the reflectors, each
feed horn can be positioned to access a
different satellite.

Tracking or moving to a different satel¬
lite can be done merely by moving the
feed horns, using low power positioners,
while additional satellites can be ac¬
cessed by adding further feed horns.

MOTOROLA REVISES
IRIDIUM PLAN

Motorola Inc has recently announced
revised plans for its Iridium system, the
proposed global telephone system based
on an array of low-earth-orbiting (LEO)
satellites. As part of the revision, the
number of satellites required has been
scaled back from 77 to 66. However the
company has also increased the number
of channels per satellite, to maintain the
system’s capacity.

The new plan is estimated to have a
cost of US$3.4 billion, a little higher than
the original estimate.

The US Federal Communications
Commission has awarded experimental
licences to Motorola and four other rival
consortia, to test their proposed systems
via a small number of satellites. One of

The Division has constructed a
prototype antenna with a 3.6m diameter
primary reflector (pictured), built
using a fast method of manufacturing
reflector panels for doubly-curved
asymmetric surfaces.

Tests have shown that the approach
yields antenna efficiencies of greater than
70% over 94% of the coverage arc.

the other proposed systems is from
Loral and Qualcomm, calling for 24
satellites and an estimated cost of only
US$1.5 billion.

SONY DEVELOPS
BLUE SEMI LASER

Sony researchers have developed a
semiconductor diode laser which
produces blue light, with a wavelength of
447nm. The diode has an active layer of
zinc selenide 48nm thick, with a layer of
zinc-magnesium-sulphur selenide on
either side — one doped to become P-
type, and the other to become N-type.

Currently the laser must be maintained
at -196°C, using liquid nitrogen. Sony’s
researchers are hopeful of developing a
version which operates at room tempera¬
ture, as the availability of a laser with

The prototype antenna is designed
for the 11 - 14.5GHz band and covers
any 20° of the geostationary arc (in¬
cluding inclined orbits up to +/-3°).
Gain at 14.5GHz is 53.3dB, and that at
llGHzis50.9dB.

Talks for commercial development of
the antenna are under way, according to
CSIRO team leader Dr Trevor Bird.

such a short wavelength would allow a
considerable increase in the amount of in¬
formation stored on CD’s, CD-ROMs
and LaserDiscs.

YET ANOTHER
VIRUS FOUND

Melbourne-based virus buster Roger
Riordan has uncovered still another nasty
virus unleashed in the IBM-compatible
DOS PC environment. Dubbed ‘Twin
Peaks’, the new nasty apparently over¬
writes the first 1310 bytes of infected
files, before displaying the message
‘Welcome to Twin Peaks. Your PC now
has the Twin Peaks Virus’.

According to Roger, initial tests sug¬
gest that the virus infects only .COM
files, but can infect read-only files. It ap¬
pears to contain code to rename files. The

124

ELECTRONICS Australia, October 1992

64Mb DRAM MADE
BY IBM, SIEMENS

IBM and Siemens have developed a
computer memory chip that can store
more than 64 million bits of data —
four times the capacity of the most ad¬
vanced memory chip used in computers
today. Their goal is to have the chip avail¬
able for mass production by the mid to
late nineties.

The new DRAM chip, which measures
10.7 x 18.1mm, can store the equivalent
of about 6000 pages of double spaced
typewritten text, and can read all 64 mil-
lion-plus bits on the chip in a fraction of a
second. The chip was developed using an
advanced CMOS technology process.
The small conductors on the chip
measure 0.4 microns in width, or ap¬
proximately 200 times thinner than a

origin is unknown, but it was found on a
Melbourne bulletin board, in a file called
M1PS.COM.

Needless to say, Roger has incor¬
porated detection for the new virus in the
latest update of his anti-viral program
VET (V7.0). However due to the way the
virus destroys file data, infected files can¬
not be repaired and must be deleted.

For information in VET, contact Cybec
on (03) 521 0655.

SANGEAN RADIO
PRIZEWINNERS

The 20 lucky EA subscribers who won
a Sangean ATS-818CS PLL synthesised
‘World Receiver’ radio in our April-June
subscription promotion, sponsored by
Dick Smith Electronics, were:

human hair. One of the smallest features
is the transistor gate insulator, which
measures only 10 nanometres thick.

The chip uses a buried-plate trench
cell. The 64-megabit chip, which
operates on a single 3.3 volt power
supply, employs many novel features
that contribute to its high performance
and reliability. Among them are bor¬
derless contacts that avoid the necessity
to provide a border around the metal that
forms electrical contacts to specific areas
of the chip.

IBM and Siemens began their joint
development on the 64 megabit chip in
February, 1990. The work is being carried
out at the IBM site in Essex Junction,
Vermont, and the IBM Advanced Semi¬
conductor Technology Centre (ASTC) in
East Fishkill, New York, in the United
States of America.

Mr J. Messenger of Goolwa Beach,
SA;

Mr R.M. Russell of Moree, NSW;

Mr Wrightson of Uriadla, S A;

Mr G.R. Skyring of Lutwyche, Qld;
Mr M. Byrne of Bundaberg, Qld;

S. Ccprow of Camberwell, Vic;
Nunawading Adventist College, Vic;
Mr D. Pulford of Forestville, NSW;
Mr D. Horsfall of Wahroonga, NSW;
Mr A.L. Birkett of Parkholme, SA;

Mr D. Gill of Berowra, NSW;

Mr R. Sbrana of Footscray, Vic;

Mr James of Eden Hills, S A;

Mr E. Dasecke of Ravenshoe, Qld;
Mrs I. Hicks of Cranebrook, NSW;

Mr D.C. James of Anula, NT;

Mr Cameron of SAS-7, Gilberton SA;
Mrs M. Dawkins of Bordertown, S A;

Mr Jones of Hamersley, WA; and

Mr S. Campbell of Hughesdale, Vic.

By now all of these winners should
be happily enjoying their new multi¬
band AM/FM radios, each of which
was valued at $399. Our thanks to Dick
Smith Electronics for making these
prizes available.

OFFSHORE ISO 9002
PCB ASSEMBLY

A competitive offshore PCB assembly
service has been introduced to Australia
by Sydney firm, Aaron Pty Ltd. A
manufacturing facility near Singapore,
under experienced Swiss management,
offers reliable low cost PCB assembly.
Working to quality standard ISO 9002,
the service includes PCB manufacture,
component sourcing and door-to-door
transport at favourable rates.

The service is ideal for businesses with
medium to large volume jobs, with
single or double sided through-hole as¬
sembly, who feel they could be more
competitive on the Australian or over¬
seas markets, or whose insertion machine
capacity is overloaded.

“Employing staff in more profitable
activities by having the run-of-the-mill
jobs executed by outside resources can
result in substantial savings and increased
competitiveness’, says Marketing
Manager Walter Schellenberg.

International clients who take ad¬
vantage of this service include Tele-
funken, Saba, Nordmende, Turner and IF.

Further information is available from
Aaron, 3/2A Pioneer Avenue, Thomleigh
2120; phone (02) 484 8244.

NASA TESTING
PERSONAL BEACONS

A group of dedicated Alaskans has
started a three year experiment that ul¬
timately could result in saving the lives of
thousands of campers, boaters and others.
The Alaskans will test the use of a small
emergency radio transmitter, known as a
Personal Locator Beacon or PLB, to com¬
municate with a 10 year old search and
rescue satellite system that, up to now,
has been used primarily for aircraft and
ship emergencies.

The experiment is being carried out
with the cooperation of NASA, the Na¬
tional Oceanic and Atmospheric Ad¬
ministration, the US Air Force and the US
Coast Guard.

The satellite system, an international
program known as COSPAS-SARSAT,
has been responsible for saving more
than 2300 lives since it was started in

ELECTRONICS Australia, October 1992

125

BNF-Fulmer, a materials research and development company based in Wantage
in Southern England ' has set up an advanced 'micro-engineering' centre to
develop small mechanical components such as pressure sensors and
accelerometers. Here a technician checks a wafer of silicon sensors.

NEWS HIGHLIGHTS

1982. Principal partners in this program
are Canada, France, Russia and the US.

The PLB program calls for four low-
Earth-orbiting satellites to be in opera¬
tion. Currently, there are six satellites —
three Russian and three US — circling
the Earth in polar orbit. However, only
four are fully operational, the other two
having lost some of their capabilities.

The North Slope Borough is one of the
most remote areas of Alaska. It covers
92,000 square miles (an area about the
size of Utah) and has what might be
described as eight towns and villages.
There are no roads to speak of, and travel
is accomplished by amphibious vehicle in
the summer and by snowmobile in the
winter, explained Charles Caldwell,
project coordinator for the borough.

Twenty beacons, which currently cost
between US$1200 and $1700, will be
used in the experiment. The beacons,
which transmit the emergency signal on a
406MHz frequency and also have a
121.5MHz signal to allow search parties
to ‘home-in’ on the location will be
loaned to qualified applicants.

AWARD TO HZ'S
'ELECTRONIC' WASHER

A new type of domestic washing
machine has won New Zealand’s premier
scientific award. The Rutherford Award
was made to the developers of the Fisher
& Paykel Smart Drive, which uses
electronics to reduce mechanical com¬
plexity to a minimum, and is powered by
an innovative long life electric motor.

In making the award to recognise in¬
novation in energy efficiency, judges said
the Smart Drive ‘uses half the electricity
a mechanical clothes washer takes for a
cold water wash’. The award was an¬
nounced to shareholders at Fisher &
Paykel’s annual meeting, where the Chief
Executive, Mr Gary Paykel, said it was a
tribute to the multi-disciplinary team who
developed the machine, which was intro¬
duced to the Australian market in May.

The meeting was told customer
demand for the machine on both sides of
the Tasman had exceeded expectation,
and production was ramping up to
produce auto washers at record rates.

The award judges, chaired by Auck¬
land University Professor John Boys,
said the Smart Drive was revolutionary
because it had the fewest moving
parts of any clothes washing machine in
the world. As well, the electronic control¬
ler constantly monitors each agitator
action and fine-tunes it to suit the
size of the load.

The innovative brushless DC motor,
moulded in high-tech thermo-plastic
polyester, which drives the agitator
directly through a single shaft, is a world
first — conceived, designed and manu¬
factured by Fisher & Paykel.

Fisher & Paykel has signed an agree¬
ment with Cameo of Canada and GE Ap¬
pliances of the United States, for both
companies to investigate the use of Fisher
& Paykel washing machine technology.

CONFERENCE TO
EVALUATE WARC '92

The Centre for International Research
on Communications and Information
Technologies (CIRCIT) in Melbourne is
holding a two day Conference in Decem¬
ber with wide ranging national and inter¬
national participation.

The participative framework of the
Conference will include:

• general and specialised users;

• new technologies and potential ap¬
plications industry/system developers
and suppliers;

• other representative interests including
policymakers, regulators, general car¬
riers; and

• other service providers in the new
competitive environments.

to service flow-ons which will be avail¬
able as a result of the decisions of
WARC ’92.

A special focus will be the new
global/regional systems, such as Low
Earth Orbit Satellites (LEOs) and Broad¬
casting Satellite Services (BSS), and
complementary terrestrial digital and
high quality systems that will service
combinations of domestic and interna¬
tional uses and potential needs.

The Conference is being held on
December 2-3, and the cost will be $595.

126

ELECTRONICS Australia, October 1992

NEWS BRIEFS

• Thomas Eectronics has been appointed as distributors in Australia for the Electrohome range
of video display monitors.

• Dr Katherine Woodthorpe has been appointed to the position of National Executive for the
Scientific Exporters Group.

• The second Australian Conference on Telecommunications Software ACTS ’93 will be held at
the Wollongong University NSW, from February 17-19. Original papers are being sought for
presentation at the conference. Further information from the Conference Secretary, I REE
Australia, PO Box 79, Edgecliff 2027; phone (02) 327 4822.

• Hypertec' s new address is Unit 4, 112-118 Talavera Road, North Ryde 2113; phone (02)
805 0111.

• As part of its export expansion plan, Melbourne-based anti-viral software developer CYBEC has
given I & J (Perak) Sdn. Bhd of Ipoh the sole rights to distribute VET within Malaysia. After only
2-1/2 years of existence, Cybec now has a staff of 10, up from four one year ago.

• Rockwell Digital Communications Division, a division of Rockwell International, has just ap¬
pointed Melbourne-based Tronic Bits as its Australian and New Zealand distributor.

For further information contact
Katherine Brain on (03) 616 8888 or fax
(03)616 8800.

OPTUS B1 LAUNCH SUCCESS

The Optus B1 satellite was launched
successfully at 9.00am on August 14.

The Chinese Long March 2E rocket
lifted off without any hitches and safely
delivered the spacecraft into low earth
orbit, approximately 200km by 1000km
above the earth. The satellite then
separated from the rocket 11 minutes
after lift-off.

At 11.00am the large solid fuel rocket
motor known as the Perigee Kick Motor
(PKM) was automatically fired for 125
seconds, sending the spacecraft into
transfer orbit (300km by 36,000km above
the earth) and on its way to the final geos¬
tationary orbit. It was expected that the
B1 satellite would reach its final orbit by
August 24.

NEW INMARSAT-A
STATION FOR INDIA

A new Inmarsat land earth station
(LES) has opened in Arvi, near Bom¬
bay, India. TTie Arvi LES, operated by
Videsh Sanchar Nigam Ltd (VSNL),
India’s overseas communications com¬
pany and Inmarsat’s Indian signatory,
is the 37th to provide access to
Inmarsat’s global mobile satellite com¬
munications network.

The LES, which will provide Inmarsat-
A services for ships at sea and users on
land, was formally inaugurated by India’s
minister of state for communications
Rajesh Pilot. Located east of Bombay, the
LES provides coverage for all of Africa,
the Middle East, Europe and most of Asia
and Australia via Inmarsat’s Indian
Ocean Region Satellite.

The Inmarsat-A mobile satellite com¬
munications system provides direct dial
telephone, facsimile, telex, e-mail and
data communications to more than

18,000 users worldwide. Although In¬
marsat-A satellite terminals have been
designed primarily for use on board
ships, land transportable models are
available for a wide range of applica¬
tions for the news media, relief workers
and others who frequently operate in
remote areas.

“The Arvi LES will be progressively
upgraded to provide high-speed data ser¬
vices by the end of this year,” said VSNL
chairman and managing director, B.K.
Syngal, speaking at the opening. “By that
time we also plan to commence Inmarsat-
C services.”

VOLUNTEERS
NEEDED BY TADVIC

TADVIC — Technical aid to the Dis¬
abled (Victoria) is looking for new volun¬
teers and clients in the Melbourne
metropolitan area and country Victoria.
TADVIC is a voluntary non-profit
cooperative, with nearly 200 members
in Melbourne and branches in Ballarat,
Bendigo, Shepparton, Geelong and
Baimsdale. New branches in the Latrobe
Valley and Mildura hope to be in opera¬
tion by the end of 1992.

Volunteers are generally qualified
tradespeople, engineers, technicians or
experienced designers and have access
to a workshop. They provide their
technical skills for free and clients are
asked to meet costs of materials and
travelling expenses.

TADVIC’s aim is to fill gaps in the dis¬
abled equipment market. If a suitable
item is not available commercially, TAD¬
VIC will usually have a volunteer able to
design and make an item to the client’s
specification. Experience with people
who have disabilities is not necessary.

TADVIC’s clients have all sorts of dis¬
abilities and come from all age groups.
Design ideas are developed by the client,
the volunteer and a TADVIC Occupa¬
tional Therapist. Clients are initially

visited where the equipment is to be used,
e.g., home, work, school, local pool,
library, shopping centre or gym. This as¬
sists greatly in getting the right design for
the situation.

Projects range from simple ‘fix-it’jobs
to more complex inventions requiring
many hours of work. All projects are su¬
pervised and coordinated by occupational
therapists employed by TADVIC.

Further information on becoming
either a TADVIC Volunteer Member or a
client can be obtained by phoning Barbra
or Philomena at the office on (03) 698
5222 (ask switchboard to put you through
to TADVIC), or by writing to TADVIC at
PO Box 88, South Melbourne 3205.

ALCATELTCCWINS
MAJOR NEW CONTRACT

A new contract to provide 2400km of
cable for SEA-ME-WE2, the longest sub¬
marine optical system in the world, has
been awarded to Australia’s Alcatel TCC,
justifying the ambitious expansion pro¬
gram launched two years ago. At that
time, the company reached a strategic
decision to increase its manufacturing
capacity to a production level of more
than 6000km per year.

This most recent order is in addition to
the 11,000km of optical cable the com¬
pany is already manufacturing for Pac-
RimEast and PacRimWest. These
systems, and the TASMAN 2 cable Al¬
catel TCC has just installed between Syd¬
ney and Auckland will form the
16,500km South Pacific Network, link¬
ing the region to the evolving global digi¬
tal network.

PacRimWest will run between
Australia and Guam, with connections to
Japan and Asia. PacRimEast will link
New Zealand with Hawaii, connecting to
North America and Europe. PacRimEast
will be operative by March 1993; Pac¬
RimWest, by December 1994.

Manufacture and installation of SEA-
ME-WE2 (South East Asia-Middle East-
Western Europe) will be undertaken by
Alcatel Submarcom of France, STC of
the UK and AT&T of America.

It will comprise over 18,000km of opti¬
cal fibre submarine cable, 160 submerged
repeaters and branching units, and 18
land based terminals in 13 sites. Opera¬
tion is scheduled for June 1994.

The portion of SEA-ME-WE2 Al¬
catel TCC will be manufacturing is
slightly longer than TASMAN 2, and
the ability to incorporate such a major
contract, while still meeting PacRim
deadlines is claimed to indicate the
level of efficiency at which the company
is operating. ♦

ELECTRONICS Australia, October 1992

127

NEW PRODUCTS

Low cost
butane torch

The Hotery MT-100/T multi-purpose
compact butane torch comes with both
needle-flame burner and soldering tip at¬
tachment, and can be used for precision
heating, soldering or as a ‘hot knife’ for
cutting plastic materials.

It uses readily available butane gas, as
used in cigarette lighters, and the inbuilt
tank can be refilled in about 10 seconds.

A knurled ring on the flow valve al¬

lows smooth and convenient adjustment
of the torch’s heating.

Available from Jaycar Electronics
stores (Cat. No. TS-1410), the torch is
priced at an attractive $12.95. Replace¬
ment soldering tips are also available, for
only $9.95.

Microwave

transmitter/receiver

Intron Electronics has released a new
range of Microwave Modules to comple¬
ment its existing Doppler Sensor produc¬
tion. The range includes a Microwave
source, a Transmitter, Data Receiver,
Receiver and a Movement Detector. All
Modules are self contained with inbuilt
antenna and control/signal conditioning
circuitry and require only a DC supply to
be fully operational.

All modules are calibrated to operate
in the ISO 2.4GHz band. They can be
used for a wide range of applications, in¬
cluding data transmission, security,
remote control, traffic control, motion
detection, moisture sensing, etc.

Evaluation kits are available and spe¬

cial designs can be produced for high
volume applications. The modules are
housed in a small plastic casing size 63 x
50 x 20mm, and connections are via a 4 x
0.1" pitch pin connector at the base.

For further information circle 242 on
the reader service coupon or contact In¬
tron Electronics, Factory 2/971 Moun¬
tain Highway, Boronia 3155; phone
(03) 720 1449.

Plain paper laser faxes

Panasonic has launched a new genera¬
tion of plain paper Laser facsimiles, of¬
fering extra features. Panafax model
UF-733, for example, offers automatic
collation so that pages are received face
down and in the correct order.

It also has a consumable status report
which indicates when toner, developer
and paper are low, so there is less
chance of machine downtime when
they need replacing.

And to ensure incoming data is never
lost during reception, the UF-733 fea¬
tures overlap printing, allowing 10mm
bottom to top overlap between split
pages.

Like the UF-733, its big brother,
Panafax UF-766 has a host of features for
its price. Fast scanning stores documents
into memory at the rate of three seconds
per page. Its dual access capability
means that you can scan documents in at
any time, whether the UF-766 is already
engaged in transmitting or receiving,
thus eliminating people needing to queue
to send a fax.

The batch transmission feature on the

UF-766 uses a program key to reserve
non-urgent documents for timer trans¬
mission to commonly used destinations.
The machine automatically brings docu¬
ments together and transmits them to the
specified station at one time, saving
money by using off peak telephone rates.

Recommended retail price for the UF-
733 laser fax is $4699, and for the UF-
766, $5999.

For further information circle 241 on
the reader service coupon or contact
Panasonic Australia, 1 Garigal Road,
Belrose 2085; phone (02) 986 7629.

128 ELECTRONICS Australia, October 1992

E24 resistors

Dick Smith Electronics has an¬
nounced the availability of the full E24
range of 0.25W metal film resistors for
immediate delivery.

The range includes all standard values
from 10 ohms to one megohm, with 1%
tolerance and lOppm tempco. Maximum
working voltages are 200V at 125°C and
250V at 70°C.

Produced by vacuum depositing select¬
ing metals and passivative materials on
to high grade ceramic rods, the devices
exceed the requirements of MIL-R-
10509F and MIL-R-22684.

For further information circle 243 on
the reader service coupon or contact Dick
Smith Electronics, PO Box 321, North
Ryde 2113; phone (02) 888 3200.

SMD trimmer pots

Murata Manufacturing has released its
range of nickel barrier layer construction
SMD trimmer potentiometers.

The RVG4H and RVG3A series ter¬
mination has a better solder wetability,
as well as higher solder leaching resis¬
tance, with its nickel barrier layer con¬
struction. It has an ultra-low profile

design with a thickness of 1.5mm, and a
light weight of 60mg and is suitable for
reflow soldering.

Also suitable for either reflow or flow
soldering is the RVG4J03/J04 series with
its low profile design (1.75mm) and the
extremely small (3.5 x 3.0 x 1.5mm)
RVG3A01 series. The resistance range
for all types is 100 ohms to 2M with a
tolerance of +/-25%, TC +/-250ppm/°C
and rated voltage of 50V DC.

For further information circle 244 on
the reader service coupon or contact
IRH Components, 1-5 Carter Street, Lid-
combe 2141; phone (02) 364 1766.

Surge protector

HPM Industries has received an
Australian Design Award from Standards
Australia for its innovative Surge Ar¬
rester. The Surge Arrester, CAT
XL777PA, has been designed to replace
an existing standard powerpoint, thereby
protecting all applicances plugged into
any powerpoint on that circuit —
upstream or downstream.

After repeated ‘clamping’ of minor

surges or the clamping of a major one,
the module within the powerpoint may
become overstressed and stop providing
protection. If this happens, a light within
the module will extinguish and an alarm
will sound. Protection is restored by
replacing the module. This does not re¬
quire calling an electrician.

For further information circle 247 on
the reader service coupon or contact
HPM Industires, 4 Hill Street, Darlin-
ghurst 2010; phone (02) 361 9999.

You can now
afford a satellite
TV system

For many years you have probably
looked at satellite TV systems and
thought “one day”.

You can now purchase the following
K-band system for only:

$ 995 .°°

Here’s what you get:

* A 1.6 metre prime focus dish
antenna, complete with all the
mounting hardware.

* One super low-noise LNB (1,4dB
or better).

* One Ku-band feedhorn and a
magnetic signal polariser.

* 30 metres of low-loss coaxial
cable with a single pair control line.

* Infrared remote control satellite
receiver with selectable IF & audio
bandwidth, polarity & digital readout.

Your receiver is pre-programmed to
the popular AUSSAT transponders
via the internal EEPROM memory.

Call, fax or write to:

AV-COMM PTY LTD
PO BOX 225,
BALGOWLAH NSW 2093
Phone (02) 949 7417
Fax (02) 949 7095

VICTORIAN DISTRIBUTOR:

L&M TV AND VIDEO SERVICES
33-35 Wickham Road
MOORABBIN 3189
Phone (03) 5531763

All items are available separately.
Ask about our C-band LNBs, NTSC-
to-PAL converters, video time date
generators, Pay TV hardware and
international TV equipment.

YES GARRY, please send me more in¬
formation on K-band satellite systems.

■m ■

Name.

Address.

1 .

.P/code.

| Phone .

ACN 002 174 478

01/92

1 _-

ELECTRONICS Australia, October 1992

129

READER INFO NO. 41

READER INFO NO. 27

NEW PRODUCTS

Dual 20W
switching PS

The FLU2-20 is a new series of low profile, dual output, 20W
switching power supplies, in a compact 75 x 130mm open
frame format with a maximum component height of 30mm.

Three models provide primary output of +5.0V at 3.0A (+/-
5% adjustable) and secondary output of 12V at 1.0A, 15V at
0.8A, or 24V at 0.5A.

High performance features of the FLU2-20 include zero min¬
imum load requirement, a universal input range of 85V AC to
265V AC and an onboard EMI/RFI suppression filter that ex¬
ceeds VDE/FCC Class B requirements by lOdB. The series of-

Low Cost Soldering Station Package

THE VERSATILE SA-572

SPECIFICATIONS — SA-572:

power switch • LED heater indication
• Variable temperature control knob
• External calibration ports
• Slim-profile iron handle with
silicone rubber grip • Flexible,
non-burn silicone iron cord
sleeve • Externally fused
• Aust. Energy Authority
Approval No. N/11933
• Closed loop
temperature control
• 315°C to 425°C

DESIGN FEATURES • Lit

• Input: 230V AC, 50/60 Hz • Iron: 70W, 230V

• Heater: Ceramic with Embedded RTD • Cord: 3-Wire, Austraian Plug

• Dimensions: 117.5mm x 115mm x 133mm • Shipping Weight: LI kg

ELECTRONIC DEVELOPMENT SALES PTY LIMITED

A.C.N. 001 363 480

Unit 2A, 11-13 Orion Road, (P.O. Box 822), Lane Cove NSW 2066

Phone (02) 418-6999 Fax (02) 418-6560

VIC (03) 764-2040 • S.A. (08) 365-1000 • OLD. (07) 254-1153

OK SS

fers short circuit and over-voltage protection, soft start and a
16ms hold-up time with 115V AC input.

Efficiency for the series is 65% typical, while the line regula¬
tion is 0.2% for the primary output of 0.5% for the secondary.

Primary load regulation is specified at 1%, with maximum
output ripple and noise at 1%, peak-to-peak. The mean time be¬
tween failures for the series is 210,000 hours.

For further information circle 249 on the reader service
coupon or contact Priority Electronics, 5/23 Melrose Street,
Sandringham 3191; phone (03) 521 0266.

PCB connectors

Viking has extended the Vitel series of connectors to include
a comprehensive range of PCB connectors in both straight and
right angle versions.

They are designed to meet the stringent demands of the
telecommunications industry, and are available in 24, 36, 50
or 64 positions, and also in right angle to standard or
reverse orientation.

The Viking connector is designed for flow soldering, and is
provided with a choice of either metric or imperial hardware (4
- 40 UNC). The connectors are easily fixed to the printed circuit
board by the use of standard or self tapping screws.

For further information circle 250 on the reader service
coupon or contact Alpha Kilo Services, PO Box 180, Lane
Cove 2066; phone (02) 428 3122. ♦

McLean Automation

Kris McLean
Phone/Fax: 045 796 365

364 Terrace Rd.,

(P.O. Box 70)

Freemans Reach. 2756

* Radio frequency systems for
switching & monitoring

❖ Custom microcontrollers

READER INFO NO. 28

130

ELECTRONICS Australia, October 1992

Within budget.
Without compromise.

With HP basic instruments,
performance costs less
than you expect.

Now you don’t have to accept
trade-offs in a basic test instrument.
Because HP offers the performance
you want at prices you can afford.

Need a dual-range output power
supply? The HP E3610 Series makes
choosing a 30 Watt DC power supply
easy-especially when you consider
the low noise and value for money
at around $460.

What about a digital multimeter for
bench or system use? The rugged 6
or 61/2 digit HP 34401A does both
with uncompromised performance
for less than $1,635.

You won’t find a better 100 MHz
digitizing scope than the HP 54600
Series. It combines an analog look
and feel with digital trouble-shooting
power for around $4,040 (2-channel)
or $4,695 (4-channel).

At less than $5,780, the HP 4263A
LCR Meter lowers the cost of
high precision 100Hz to 100kHz
benchtop and system component
measurements.

And the 8-function HP E2373A is
just one of the HP E2300 Series
3 1/2 digit handhelds priced from
$160 to $310.

For more information, call our
Customer Information Centre on
008 033 821 or Melbourne 272 2555,
and we’ll send you a data sheet that
shows how affordable performance
can be.

A Better Way.

Wha% HEWLETT

mLHM PACKARD

Prices exclude sales tax.

Test and Measurement Feature

The latest test and
measurement products

Economy 60MHz,

20MHz scopes

Dick Smith Electronics has announced the release of
four new oscilloscopes, enhancing its range of Digitor test
instruments.

The new models include an economical 20MHz base model
analog unit; fully featured 20MHz and 60MHz analog instru¬
ments; and an advanced 20MHz analog/ digital model.

The full featured 20MHz and 60MHz models offer com¬
ponent test, beam find and dual timebase facilities, in addition
to the usual functions, while the 20MHz digital storage/analog
model also features dual 2k x 8 trace buffers with trace roll,
save and plot facilities. Prices for the four models range from
$699 to $1599.

For further information circle 201 on the reader service
coupon or contact Dick Smith Electronics, PO Box 321, North
Ryde 2113; phone (02) 888 3200.

Single phase power meter

Yokogawa has released a new single-phase high accuracy
A C/DC power meter, intended for appliance power consump¬
tion and single-phase power distribution measurement.

Known as the 2534, the new meter is capable of measuring
AC and DC power at levels of up to 600V at 20A, to an
accuracy of 0.5%. The measuring range is selected automat¬
ically, or may be manually controlled. An unusually wide AC
input bandwidth of 10Hz to 20kHz allows more accurate
power measurement, even in the presence of complex current
waveforms such as caused by PCs, fax machines or TVs.

In addition to measuring voltage, current and power, the
2534 can also measure and display apparent power, reactive
power, power factor, phase angle, watt hours and frequency
from 4Hz to 22kHz. A memory card interface is provided
allowing readings to be saved and later plotted, or loaded into
a PC. Optional RS232 and GPIB interfaces are also available.

Fur further information circle 202 on the reader service
coupon or contact Yokogawa Australia, Private Mail Bag 24,
North Ryde 2113; phone (02) 805 0699.

Ultrasonic

measurement system

A new measurement system called V-
Scope makes it possible to measure
position, velocity and acceleration
without the need to run wires or
cables to the object whose motion is
being measured.

The system is analogous to a satellite
tracking system. A transponder attached
to the body sends ultrasound signals
which are received and processed by V-
Scope components. These signals are ac¬
tivated by an infrared signal sent from a
button on the transceiver tower.

There are three systems available: the
VS-40 which can monitor one to four
bodies in a single axis, with a maximum
sampling rate of 50Hz; the VS-100
which can also monitor up to four
bodies, but in one, two or three dimen¬
sions, at up to 100Hz; and the VS-
110PRO for up to eight bodies in one to
three dimensions, at up to 200Hz sam¬
pling.

An individual transponder button is
required for each body being monitored,
as well as a separate tower for each
dimension. So the VS-40 has one tower
only for ID motion, whereas the other
two systems have three.

The information is first processed by
the V-Scope microcomputer (which con¬
tains a Motorola 68000 microprocessor),
and then connected via the RS232 serial
port to an IBM PC or compatible for fur¬
ther processing. As well as logging the
information, the PC can also be used to
control the V-Scope microcomputer in
its ‘slave’ mode.

The VS-40 configuration costs $850,
the VS-100 $4850, and the VS-
110PROF $9071. The VS-100 can be
purchased in a simplified ID version, the
VS-100/1 for $2564, and later upgraded
for full 3D measurements. The quoted
prices include transport costs.

132

ELECTRONICS Australia, October 1992

For further information circle 203 on
the reader service coupon or contact
IDM Instruments, 6 Carmen Stree, Dan-
denong 3175; phone (03) 706 7837.

Polyphase
calibration source

University Paton Instruments (UPI)
has released a new Australian designed
and manufactured precision DC/AC
polyphase calibration source.

This new unit, called the ‘Examiner
Series 3001’ has been designed in col¬
laboration with the CSIRO’s National
Measurement Laboratory, and will be a
valuable instrument for laboratories who
test and calibrate electrical instruments.

The calibration source combines into
one compact unit a polyphase current
and voltage standard. Its features in¬
clude: excellent stability (20ppm); 0.5%
accuracy; DC to 100kHz; voltages to
300V phase-to-neutral, 150VA per
phase; and currents to 20A (200VA per
phase).

The source is also capable of generat¬
ing arbitrary waveforms, and the calibra-
«tion of single and three-phase indicating
and measuring instruments and trans¬
ducers, including power and energy.
Designed as a fully integrated system,
the Examiner series 3001 gives control
of all parameters, including phase of all
vectors. It is operated via a friendly
graphical user interface on a PC.

For further information circle 205 on
the reader service coupon or contact
University Paton Instruments, PO Box
402, Riverwood 2210; phone (02) 534
6100.

Digital barometer

Vaisala’s Digital Barometer PA 11 is a
precision instrument, providing accurate
and reliable barometric pressure meas¬
urements over the range of 800 to
1050hPa.

The PA 11 consists of three inde¬
pendently operating aneroid capsules
and transducers, controlled by a micro¬
processor. Triple redundancy ensures ex¬
cellent long term stability and measure¬
ment accuracy, even in the most
demanding applications. Each pressure
transducer is an aneroid capsule with
capacitive elements, installed in a vac-
cum inside the aneroid, with a pressure-
frequency converter controlled by the
microprocessor. The aneroid capsule
temperature is measured by an internal
temperature sensor providing accurate
compensation.

The 10 - 28V DC powered barometer
has a 4.5 digit liquid crystal display with
12.5mm high digits. It can display the

High resolution
counter/timer

Thurlby-Thandar’s new TF830 high
resolution counter timer uses the
reciprocal frequency counting technique
to achieve high resolution at all frequen¬
cies. The system yields at least seven
digits of resolution per second of meas¬
urement time, and can measure low fre¬
quencies to a resolution of O.OOlmHz.

The TF830 is also available with the
optional RS232 interface, conforming
with the Thurlby-Thandar ARC system
(addressable RS232 chain).

All front panel functions can be
remotely controlled and measurements
can be read back to the controller. This
makes it suitable for use in a wide
variety of automatic measurement sys¬
tems.

In addition to frequency measurement

three hourly pressure trend with a
plus/minus sign to indicate increasing or
decreasing pressure. An audio alarm in¬
dicates low battery voltage or an out-of¬
range transducer.

Interfacing to printer, computer, ter-

up to 1.3GHz, the TF830 offers period
measurement, frequency ratio, pulse
width measurement and event counting.
Pulse width measurements can be made
from rising to falling edge, or vice-versa.

Using input socket A, frequency can
be measured from 5Hz to 25MHz, with
resolution O.OOlmHz to 100Hz. Socket
B measures frequency from 20MHz to
1.3GHz, with resolution from 1Hz to
10kHz.

Period can be measured from 10ns to
lus, pulse widths from lus to 26s, with a
resolution of 100ns. Using sockets A and
B, the ratio of two frequencies is dis¬
played as eight digits. The TF830 can
operate from disposable batteries or AC
line.

For further information circle 204 on
the reader service coupon or contact Nil-
sen Instruments, 200 Berkeley Street,
Carlton 3053; phone (03) 347 9166.

minals, automatic weather stations is by
a standard serial output.

For further information circle 206 on
the reader service coupon or contact
Vaisala, 4/8-12 Sandilands Street, South
Melbourne 3205; phone (03) 696 5699.

ELECTRONICS Australia, October 1992

133

READER INFO NO. 29

P/C MULTIMETER
& DATALOGGER

P/C/ software supplied provides:

Storage up to 250 hours.
Digital display.

Graph display.

Print from PCX file.

Multimeter Features

autoranging 3 3 /* display.

41 Point bar graph with zoom and null.
Maximum, minimum, average and
relative reading.

DC & AC volts/amps. ohms,
transistor gain, diode, frequency,
capacitance. DB’s and audio power

For ordering and further information call or fax the authorised
distributor;

ZENOLOGY SALES P/L. ACN 050 551 84 7

7/245 Springvale Rd, Glen Waverley, Vic. 3150.

PHONE (03) 802 0599. FAX (03) 803 4146.

Test & measurement products

Electrostatic voltmeter

Monroe Electronics’ model 263 high speed electrostatic volt
meter uses a hybrid circuit which combines DC electrometer
techniques with AC chopper circuitry, to produce an extremely
high speed instrument for accurate measurement of electros¬
tatic and other high impedance sources, without physical con¬
tact. Response rates faster than 50 microseconds are possible.

The model 263 incorporates a model 1027 probe, which con¬
sists of a standard tuning fork and wideband preamplifier.

This small probe (7.9 x 7.9 x 73mm, with a 1.75mm aperture
diameter) is available in both end and side viewing configura¬
tions. High resolution and transparent probe configurations are
also available.

The range of the model 263 is to 2kV, with autopolarity with
a 0.1% accuracy (DC). Readout is via a large digital LCD
display, and a recorder output is also provided. Instrument drift

is quoted at less
than 0.01V per
hour, after one
hour warm up.

For further in¬
formation circle
207 on the reader
service coupon or
contact Zenology
Sales, 245 Spring-
vale Road, Glen
Waverley 3150;
phone (03) 802
0599.

All Prices inclusive of Sales Tax

Government and Education
Prices Available

★ TEST OUR PRICES ★ MEASURE THE VALUE

MODEL: SG-4162AD $445

I RF SIGNAL GENERATOR/COUNTER

GENERATOR:

I Freq Range IOOKHz-150MHz in 6 Ranges; RF

I Output 100 m Vrms. Modulation lnt.1KHz(30%).
f Ext 50Hz-20KHz; X tal OSC 1-1 5MHz(HC-6U)

FREQ. COUNTER

Freq Range 10Hz-150MHz; Gate Time 1S.0.1S;
Accuracy ± 1 Count; Sensitivity 35m V-50mV
(10Hz-150MHz)

MODEL: AG-2603AD $445

, * AUDIO GENERATOR/COUNTER

GENERATOR:

i!B Freq Ran 9 e 10Hz-1MHz; Wave Form Sine/Square;

IBB Output Level Sine: 8 Vrms. Square: 10 Vp-p;

Attenuator 0. -20dB, -40dB and Fine Adiuster

w - SmM Br FREQ C0UNTER

Freq Range 10Hz-150MHz; Gate Time IS. 0.1S;
Accuracy ± 1 Count; Sensitivity 35m V-50mV
(10Hz-150MHz)

DP* rr T

MODEL: SG-4160B $253

RF SIGNAL GENERATOR

Freq Range IOOKHz-150MHz in 6

Ranges

RF Output 100 m Vrms

Accuracy ± 3^o

Modulation Int. lKHz(30^»)

Ext.50Hz-20KHz

Xtal OSC l-!5MHz(HC-6U)

Attenuator Hi-Lo(-20dB)

MODEL: AG-2601 A $253

7 — £ M AUDIO GENERATOR

Freq. Range 10Hz-1MHz

Accuracy ±3% + 2 Hz

w. J| Wave Form Sine/Square

/ Output Level Sine: 8 Vrms

■■ “ ... ^ Square: lOVp-p

m • • * | jjk Attenuator 0.-20dB,-40dB and

Ww W prine Ad J us,er

POWER SUPPLY (SINGLE OUT-PUT)

POWER SUPPLY (DOUBLE OUTPUT)

Model

Constant

Price

Voltage (CV)

Current (CC)

PS-303

0-30VDC

0-3A

$270

PS-305

0-30VDC

0-5A

$312

8110

0-60VDC

0-3A

$430

8112

0-60VDC

0-5A

$545

Over load and short circuit protection
Current can be limited from 0-3A or 5A

Model

Constant

Price

Voltage (CV) Current (CC)

PS-303D

± 0-30VDC

0-3A

$503

PS-305D

± 0-30VDC

0-5A

$530

8108

± 0-60VDC

0-3A

$722

8109

± 0-60VDC

0-5A

$943

Over load and short circuit protection
Current can be limited from 0-3A or 5A

134

ELECTRONICS Australia, October 1992

Noise factor meter, source

Hewlett-Packard has introduced two noise-figure-measure-
ment products that aid in design and production test for direct
broadcast satellite (DSB) and personal communications net¬
work (PCN) system applications. The products are the HP
8970B Option 020 noise figure meter, which has an extended
input-frequency range of 10MHz to 2.047GHz, and the HP
346B Option H42 noise source, which offers major improve¬
ments in noise-figure accuracy for the 10GHz to 15GHz DBS
frequency range. The new products make more precise charac¬
terisations of low noise block downconverters (LNB) with al¬
most a 2-to-l improvement in measurement uncertainty.

The HP 8970B Option 020 performs high-accuracy noise-
figure measurements on components for direct broadcast satel¬
lites to 2.0476Hz with lower measurement uncertainty, as well
as eliminating the need for a costly and complex external
downconverter. To match the new 2.0476Hz intermediate fre¬
quency (IF) of a LNB, users previously required an external
instrumentation local oscillator/downconverter to extend the
1.6GHz upper limit of HP’s previous model.

Major features included in the new meter include simul¬
taneous gain and noise figure measurement, second-stage cor¬
rection, low-instrumentation uncertainty (<0.1dB) and
automatic local-oscillator control. For PCN applications, it can
also be used for cellular radio systems that operate in the
1.96GHz frequency band, such as digital Europe cordless
telephone and Japanese digital cellular. Because it can make
direct noise figure characterisations of cellular receivers and
components without external downconverters, it provides a
distinct cost advantage for the customer.

The price of the HP8970B Option 020 is $21,300 and the HP
346B noise source is $2700. ❖

AUSTRALIAN MADE

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FRESH IN THIS MONTH

FLUKE 8375a 5’/* Digit DMM + T RMS $375—

FLUKE 8040 Like 8050A $365—

FLUKE 8800A 5Va Digit DMM (Port) $375—

HP 721A 0 —30V D C. Power Supply $75—

TEK 7904 500 MHz Oscilloscope frame with 400 MHz 2 channel vert,
and Time base $1,950—

Perkin Elmer A.A. Spectrophotometer with flame and furnace + Software
and Accs BRAND NEW! Maybe worth $30k+ $6,750-

Sweeny ELECTROSTATIC Voltmeter 0-50Kv (NEW) $275—

Limit one each above per customer

OTHER LINES!

Capacitor Decade Box 60 mFd
DANA 50 MHz 2 ch Timer Counter
Allison H P & L P Audio Filter
HP 41 5D 'WR Meter
HP 415E SWR Meter
DAVEN 100 db 50uz Switch Atten
TRANSCO Motorised R F Switch
R&S AM/FM IF Sig Gen 4-300MHz

$60

$100

$60

$150

$250

$80

$75

$180

H P 680 Strip Chart Recorder $30

Telonic R F Sweeper 0- 1 5GHz $575

Trimoix GIB lOKv Breakdown Tester $75

H P 7035B XY Analog Recorder $60

HP 8731B Pm Modulator 8 2 4GHz $60

GR 161 7 Capacitor 8ridge $350

H P 7100B M Strip Chart 2 pens $40

R&S Polyscop II Swob 1000MHz Spec An $30

WE STOCK 240V110V TRANSFORMERS, Most TEK 500 Senes Modules,
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SPECIALISTS IN NEW AND USED SCIENTIFIC EQUIPMENT

26 Fulton Street, Oakleigh South, Vic. 3167. Ph: (03) 562 9500 Fax (03) 562 9615.

READER INFO NO. 30

ELECTRONICS Australia, October 1992 135

READER INFO NO. 31

Test and Measurement Feature:

Modern RF Signal
Generators & their use - 2

In this second of three articles adapted from a seminar given by engineers at Marconi Instruments in
the UK, we discuss the various performance parameters by which an RF signal generator is judged.
This covers aspects such as frequency stability, distortion, spurious signals and incidental com¬
ponents, sideband noise and residual modulation.

The design of a signal generator is a
delicate balance of performance and
cost, and limitations in the performance
of instruments are inevitable. Some of
these limitations are due to fundamental
physical constraints (e.g., thermal noise)
whilst others are related to the design
itself. Since the perfect signal generator
does not exist, users have become accus¬
tomed to accepting some limitations in
the interest of obtaining an economic
solution to their needs. In addition to in¬
accuracies caused by imperfections in
the instrument, other errors can be intro¬
duced by the operator in the way the unit
is connected to the device under test.

Some of the errors due to instrumenta¬
tion inaccuracy can be allowed for by
making measurements with other instru¬
ments. For example the modulation
depth of a signal generator could be
checked with a modulation analyser
when a more accurate result is required
(e.g., in ELS test applications). Whilst
this correction technique can work for
some parameters, it cannot improve the
performance in areas such as distortion
and noise.

Frequency stability

Frequency stability can be defined as
the degree to which an oscillating source
produces the same frequency throughout
a specified period of time. Every RF
source exhibits some amount of frequen¬
cy instability. This stability can be
broken down into two components —
long term and short term.

Short term frequency stability con¬
tains all elements causing frequency
changes about the nominal frequency of
less than a few seconds deviation, and is
often seen as residual modulation com¬
ponents. Long term stability describes
the frequency variations that occur over

long time periods, expressed in parts per
million per hour, day, month or year.

Short term stability consists of
randomly fluctuating phase noise
terms which can be observed on an
ideal spectrum analyser (one which
has no sideband noise of its own).
There are two types of fluctuating phase
noise terms:

1. Deterministic — discrete signals ap¬
pearing as distinct components in the
spectral density plot. These signals,
commonly called ‘spurious’, can be
related to known phenomena in the
signal source such as power line fre¬
quency, vibration frequencies, or
mixer products.

2. Random — commonly called ‘phase

noise’. The sources of random
sideband noise in an oscillator in¬
clude thermal noise, shot noise and
flicker noise.

DC coupled frequency modulation
systems can also give rise to instability,
as the method of producing this type of
modulation usually requires that the
phase locked loop which controls the
stability is unlocked to allow the fre¬
quency to be directly controlled by an
external voltage. In earlier signal gener¬
ators the selection of ‘DC coupled FM’
caused an offset in the carrier frequency,
which was followed by a gradual drift of
up to 100Hz per hour. When testing
narrowband radio equipment the offset
and the drift cause measurement

136

ELECTRONICS Australia, October 1992

problems, and in some cases operators
find it necessary to connect external
equipment to their signal generators to
determine the amount of drift so that
they can compensate for it.

Fortunately with the later generator of
synthesised signal sources the offset and
drift problems have been virtually
eliminated.

With regard to long term stability most
modem signal generators use a crystal
oscillator as their primary frequency
reference, and such oscillators exhibit
a gradual change in frequency with
time as the crystal ages. This drift is
usually in an upward direction (i.e., the
frequency of die oscillator rises with
time). Some means for resetting the os¬
cillator is always provided and a facility
for using an external frequency refer¬
ence, such as a signal produced by a
rubidium or caesium beam oscillator, is
normally provided.

Distortion

Harmonics of the carrier frequency
usually do not cause measurement
problems, but if necessary they can be
suppressed using a low-pass filter to
pass the wanted frequency and eliminate
all the unwanted harmonics. Distortion
of the modulating signal may be reduced
by substituting a low distortion oscillator
in place of the standard internal oscil¬
lator, but the distortion associated with
the actual modulation circuits cannot
easily be removed and must be accepted
as a fundamental limitation of the
design. If better performance is needed,

the user will need to identify an instru¬
ment with a better specification.

Modulation distortion associated with
AM (see Fig.2.1) can sometimes be ob¬
served using a spectrum analyser, but
care should be taken when interpreting
the results as the presence of small
amounts of FM will also give rise to
sidebands which occupy the same posi¬
tion as the AM distortion sidebands.

With frequency modulation the effect
of distortion cannot be seen on a
spectrum analyser and a linear
demodulator must be used to provide a
signal which can be interpreted by a
distortion analyser. In most applications
the level of distortion introduced by
modem signal generators when used in
the FM modo can be considered to be
negligible, for all but the most demand¬
ing applications.

Spurious signals

The modem signal generator is usual¬
ly based on a frequency synthesised os¬
cillator, and may also contain mixers,
multipliers and dividers to extend the
frequency coverage.

These components will inevitably in¬
troduce unwanted spurious signals,
and the instrument will contain filters
and buffering circuits which are
designed to reduce the level of the sig¬
nals that are products.

A major problem with these spurious
signals is that the position of the com¬
ponents cannot easily be predicted by
the user. The presence of such signals
limits the ability of the generator when

used for testing the out-of-band perfor¬
mance of a receiver, and if the level of
these components is particularly high, it
is even possible that the in-band perfor¬
mance measurements will also be sub¬
ject in error.

Non-harmonically related signal
products may be removed by careful fil¬
tering, but this is likely to be impractical
if measurements need to be made at a
number of different frequencies. The
only satisfactory solution is to use a
source with a performance which is at
least lOdB better than the receiver meas¬
urement requirement, or to use an instru¬
ment which produces its output without
the aid of mixers.

Incidental components

When a signal source is producing
amplitude modulation, imperfections in
the modulation circuits and the RF
amplifiers will cause small amounts of
FM to be produced at the same time.
Similarly, AM components will be
produced by imperfections in an oscil¬
lator system which is designed to pro¬
vide frequency modulation.

These incidental FM on AM and AM
on FM components limited the useful¬
ness of the generator, when measuring
the ability of a receiver to reject un¬
wanted modulation, and there is no
simple way of improving the perfor¬
mance of an instrument for this type of
test. Again, the only satisfactory solution
is to use an instrument with a perfor¬
mance which comfortably exceeds the
required receiver measurement value.

Residual modulation

When measuring receiver signal to
noise ratio, the user will switch the gen¬
erator modulation on and off to record
the ratio of the two receiver output
values. Any noise modulation com¬
ponents which remain when the
modulation tone is switched off will in¬
evitably limit the measurement ability,
and it is possible that the ratio measured
is not the receiver performance, but that
of the generator.

Residual modulation due to noise will
always be present on any signal source
and will be specififed, although the
bandwidth in which it is measured may
be different from that of the receiver.
Residual components due to AC power
line frequencies will also be present, but
their effect will usually be small com¬
pared with the noise.

Reduction of residual components is
rarely possible, but it is worth checking
that hum fields from nearby equipments
are not increasing the problem. If this
fails to produce the necessary improve-

ELECTRONICS Australia, October 1992

137

Modern RF Signal Generators and their use - 2

ment, the only alternative is to use a sig¬
nal source with a better performance.

Sideband noise

The unmodulated output from a signal
generator is often thought of as a single
spectral line, but in reality the output
spectrum is spread across a wide range
of frequencies. Conventionally the noise
distribution of the signal is specified in a
1Hz bandwidth and curves are often
given which show the way this noise
varies with offset from the carrier (see
Fig.2.3).

Close to the carrier the level of the
noise sidebands will be related to the
design of the RF oscillator in the gener¬
ator, but at larger offsets the noise falls
to a constant level which extends across
the full range of the instrument.

The sideband noise of a signal gener¬
ator limits its ability to measure the
adjacent channel rejection of narrow-
band receivers, since the noise will be
detected by the receiver and may
lead to a lower apparent rejection value
being indicated.

The use of filters to remove
sideband noise is impractical, because of
the circuit complexity needed to achieve
the necessary reduction of sideband
noise without suppressing the carrier
and its modulation components. If
sideband noise is limiting the measure¬
ment, the only real solution is to use a
better signal source.

Sideband noise characteristics of dif¬
ferent types of generators vary widely,
and in general it is true that the noise

produced by a low cost generator will be
higher than that produced by a high
priced unit.

Conversion of sideband noise figures,
usually given in dBc/Hz, to assess the
available adjacent channel rejection
measuring ability is a complicated exer¬
cise as the user needs to take into ac¬
count the receiver bandwidth, the
channel spacing and the shape of the
generator curve, but as a simple ap¬
proximation 52dB should be subtracted
from the modulus of the sideband noise
figure at the required channel spacing.

For example a generator with a
specification of -122dB/Hz at 20kHz
offset would give an adjacent channel
measuring capability of 70dB (122 - 52)
and a generator with a rated perfor¬
mance of -146dB/Hz would allow ad¬
jacent channel measurements of up to
94dB (146 - 52).

Level inaccuracies

The output level of a signal generator
often covers a range of over 140dB, and
very careful attenuator design, construc¬
tion and testing is needed to provide the
best overall accuracy. Inaccuracies at
high output levels may be allowed for by
checking the output with an accurate
power meter or voltmeter, but at low
levels the user is unlikely to have access
to test equipment which can make meas¬
urements with the required accuracy.
Since the user has no way of improving
the accuracy at these low levels, there is
no alternative but to allow for the rated
inaccuracies of the source.

Connection errors

In addition to errors caused by limita¬
tions of the generator performance, inac¬
curacies also occur because of the
connections between the source and the
unit under test. Obvious problems occur
because of the use of poor quality cables
or connectors, and because of inac¬
curacies associated with any matching
units or attenuators that are used. These
problems can usually be minimised or
their effect allowed for.

A less obvious effect is caused by the
impedance mismatch which will often
occur between the signal generator and
the device being tested and in extreme
cases this can introduce additional errors
as high as +/-ldB. This type of error can
be reduced by the simple technique of
connecting a good quality 20dB at¬
tenuator pad between the generator and
the item under test

User aspects

Although technical performance often
dominates the decision making process
when selecting a signal generator, con¬
sideration also needs to be given to
aspects related to the ease of use and the
long-term cost of ownership.

Units which are difficult to operate
will inevitably cause problems when
used by inexperienced operators, and
even experienced engineers have been
known to have difficulties when using
features which they rarely access.

Other criteria of importance may be
the number and type of modulation os¬
cillators available. One kilohertz and
400Hz are usually sufficient for the
standard receiver tests, but further tests
require other frequencies — for ex¬
ample, when measuring the AF
response. In addition to the functional
features of a product, the user also needs
to give careful thought to the long-term
support of the unit.

Most organisations now insist that
their test equipment is calibrated on a
regular basis, so that they can maintain
the quality of their own operation.
Calibration costs money, and the faster it
can be done the lower the overall cost
will be. Most modem signal generators
can be tested automatically using GPIB
control and in some units the adjustment
of the performance can also be handled
by bus control, providing a further
potential cost saving.

The third and final article in this
series will describe the use of a signal
generator to measure the performance
of a receiver. ❖

SSB noise dBc/Hz

-60

-70

-80

-90

-100

-110

-120

-130

-140

-150

-160

0 .<

>1 0.1 1 10 100 1,000 10,000
Frequency offset (kHz)

Fig.2.3: Typical SSB noise curve of a synthesiser.

138

ELECTRONICS Australia, October 1992

SIEMENS

PCM 30 analyzer K 4304

Now with remote monitoring

□ Detection of CRC4 errors

□ Drop and insert functions

□ Bit error evaluation in accordance
with CCITT Recommendation
G.821

□ Testing of regenerative repeaters

□ External printer port

□ Remote monitoring via V.24
interface

Soon you will never want to be without
the K4304 again. Partly because you
can always take it with you wherever
you go to make bit error
measurements in 2-Mbit/s systems. But
especially because the K4304, despite
its small size, has a performance equal
to that of large units. It is transmitter
and receiver in one. It diagnoses

during operation — as an in-service
monitor for 2-Mbit/s transmission
routes and their 64-kbit/s channels.
And it can operate out of service as a
bit and code error tester.

Its individual features:

□ in-service: Bit error measurements
from the frame alignment signal and
code error measurement

Siemens Ltd
885 Mountain Hwy
Bayswater 3153
Ph: (03) 721 2510
Fax: (03) 721 2500

Siemens test
equipment

for reliable
communications

READER INFO NO. 34

Test and Measurement Feature:

Handheld DMM and
1.2GHz frequency counter

Jaycar Electronics now has available two interesting digital meters. Its latest multimeter model in¬
cludes — as well as the usual ranges — measurement of frequency, capacitance and temperature
and inductance. The company is also offering a very compact handheld frequency counter, which
covers a wide spectrum from 10Hz-1.2GHz.

The new multimeter, model TES-
2360, has a 3-3/4 digit (reads up to
3999) liquid crystal readout, and in ap¬
pearance is very similar to many other
meters on the market. It uses a 30-
position rotary switch, combined with
three slider switches (‘on-off’, ‘DC-
AC’ and ‘hold’), to allow selection of
the various ranges.

Four sockets are provided at the bot¬
tom of the case for 10A, mA/uA, Com¬
mon and V/ohms. (Though not labelled
on the meter, the V/ohms socket is also
used for frequency, temperature and
logic level measurements.)

However, the meter uses special
sockets for measuring both
capacitance and inductance. These are
slit sockets at the left side of the front
panel, which allow component leads to
be inserted directly into spring con¬
tacts to minimise test lead errors.

Readouts for this very versatile meter
are via 16mm digits, which appear to be
larger than usually provided Its clear,
uncluttered display is very easy to read.
As you would expect these days on
any reasonable model, the meter fea¬
tures autopower-off (after 30 minutes),
low battery and overload indications,
and diode testing combined with a
continuity buzzer.

The meter is protected by a solid case,
which is fitted with a tilt stand. The case
also has two grooves, one at each side of
the display, into which you can also slide
the base of the general-purpose test
probes provided.

You can use this handy facility to
make a probe extend beyond the top of
the meter for single-handed measure¬
ments or, by inverting the probe, for
storage.

The rotary switch gives you access to

five ranges for both DC and AC vol¬
tages: 400mV, 4V, 40V, 400V and
1000V/750V (DC/AC). The DC ac¬
curacy is (±0.5% + 1 count) on all ran¬
ges, with the AC accuracy being l%+3
for the first four ranges and 1.2%+3 for
750V.

Similarly, there are four current ran¬
ges: 400uA, 40mA, 400mA and 10A.
The DC and AC accuracies for the first
three ranges are 1%+1 and 1.2%+3
respectively; while for the 10A range
they are 1.2%+1 and 1.5%+1.

Resistance is measured over six ran¬
ges: 400 ohms, 4k, 40k, 400k, 4M (all
0.8%+2 accuracy), and a high 40M
(1.5%+2). Frequency is measured over
four ranges: 4kHz, 40kHz, 400kHz and
4MHz (all at 0.5%+l), with a maximum
input sensitivity of IVrms and a maxi¬
mum applied voltage of 350Vrms.

An accuracy of 5%+10 applies to the

140

ELECTRONICS Australia, October 1992

five ranges for both capacitance and in¬
ductance. These ranges are: 4nF, 40nF,
400nF, 4uF and 40uF; 4mH, 40mH,
400mH, 4H and 40H. And the accuracy
for the temperature range of -40° to
+150°C is ±3°. (The display can be in
either Celsius or Fahrenheit — for °F the
accuracy is ±5°.) A special temperature
probe (with a diode sensor) is provided
for these measurements.

How it performed

With a few exceptions for larger
AC currents, all the measurements
which we made were well within the
stated tolerances.

Four volts-DC measurements were
made, in the range 200mV-10V, with a
Fluke model 8050A being used to
calibrate our standards.

Five volts-AC readings were also
made (200mV - 32V), along with five
amps-DC (400uA - 100mA) and six
amps-AC (400uA - 1A). This last men¬
tioned current reading produced a meas¬
urement error of -5.1%, which is well
outside the quoted 1.5%+3.

Two further AC current measurements
were made on the 10A range, and check¬
ed with a Goldstar DM, model 6335. A
5A and 10A reading on the TES-2360
produced errors of -1.80% and -1.91%,
respectively. Both these readings are just
outside the quoted accuracy.

Seven resistance readings from 100
ohms-393k and 11 capacitance read¬
ings from InF - lOuF (checked against
an HP 4263A meter) proved accurate,
along with five frequency readings
from 5kHz - 2.5MHz (checked against
a Goodwill GFC 8100G reference).

We were unable to check the induc¬
tance ranges, not having any suitable
standards. Likewise for the temperature
range — though a check against a
laboratory mercury thermometer gave
DMM readings in icy water of 5.9°C
(3°C); room temperature, 24.3°C
(24°C); and hot water, 69.5°C (72°C).
So compared with the mercury ther¬
mometer, all readings were within the
stated ±3°.

We noticed that the temperature probe
seemed to be slower in coming to its
final reading for the colder temperature
than for the hotter one, taking about an
extra minute to settle.

Frequency counter

The model WFC-308 Wisher frequen¬
cy counter is very compact, with the
case measuring only 130 x 80 x 35mm,
and weighs 350g.

It is powered by an 8.4V rechargeable
battery, which requires a 12V/500mA
plugpack for recharging. The battery can

give over four hours of operation. The
counter has an eight red-LED digit dis¬
play for its two ranges. A three-position
slider switch combines the on/off switch
and range selector.

Range A is MHz (20MHz - 1.2GHz),
with three gate times of 2.56s, 0.25s and
0.02s (selected by a second slider
switch), while range B is kHz (10Hz -
20MHz) with its gate times of 2s, 0.2s
and 0.02s.

Input impedance is 50 ohms (range A)
and lM//80pF (range B), with the maxi¬
mum input voltage being 5Vp-p and
IOOVp- p, respectively.

The sensitivity for the B range is
quoted at <15mV from 10Hz - 20MHz;
and for the A range <21mV from
200MHz - 1.0GHz. This figure increases
as you move towards the top and bottom
of the range, reaching <22mV for
1.0GHz - 1.05GHz and <185mV for
21 MHz - 26MHz.

Test results

Our standard for the frequency meas¬
urements was a 5MHz signal produced
by an HP crystal-oven VXO. This was
checked against a 5MHz VNG com¬
munications channel, and produced a
beat frequency of less than 2Hz. This
provided more than adequate accuracy
to test the WFC-308.

The basic stability of the counter over
several hours proved to be about 2ppm,
comfortably within the 4ppm specifica¬
tion. Interestingly, the meter under-read
only for the first five - six minutes, after
which it over-read with a continuously
increasing inaccuracy.

So, for practical use, after about five
minutes heating, the meter should
operate with its maximum accuracy.
This makes it very useful for field meas¬
urements, where quick readings are re¬
quired and the meter is normally
switched off when not in use.

The sensitivity of the readings was
also checked. On the B range, 10MHz
and 20MHz both recorded about
lOmVRws; while on the A range, the
results were 18mV (25MHz), 6mV
(100MHz) and 5mV (500MHz). These
were all well lower than quoted sen¬
sitivities.

With no input on the higher range, the
pre-scaler chip self- oscillated — not un¬
usual — and typical input signals easily
over-ruled the oscillations, so this was
not a problem.

Finally, testing a 500MHz signal with
the three gating positions gave readings
of 501.1479 (2.56s), 501.147 (0.25s) and
501.15 (0.02s).

These results were as expected, but
were done because of a confusing para¬

graph in the manual saying that the
readout on range B (actually range A!)
needed to be divided by ‘10’ — it
doesn’t!

Inside the case

Two self-tapping screws secure the
front and back sections of the sturdy
case of the meter, which is further held
by two plastic clips. This makes it quite
difficult to open when you don’t realise
what is still holding the sections
together.

Inside the case, the rechargeable bat¬
tery takes up over 50% of the space, oc¬
cupying the bottom half. The top half
has a metallic shield and one PCB which
holds all the electronic components.
Near the bottom of this board are the
two crystals (one for each scale), along
with their calibration trim capacitors.

Summary

The major advantage of the TES-
2360 DMM is obviously the additional
ranges that it offers. It offers all the
usual tests, plus frequency, inductance,
capacitance and temperature — quite
an impressive array. And the tempera¬
ture probe reacts quite quickly to
temperature changes.

In favour of the frequency counter is
its very compact size, and its ability to
be used in the field, allied to its large
frequency range — up to 1.2MHz. We
believe both meters represent good
value for money.

But why do the manuals of such
Taiwanese products have to contain so
many spelling mistakes and contradic¬
tory information?

For example, the counter panel
labels range B the lower band, while
the manual reverses this; and there is
the confusing ‘divide by 10’ instruc¬
tion for the higher frequency range.

Also, the DMM manual gives two sets
of data for the temperature probe, quot¬
ing accuracy as ±2°C in the first and 3°
in the second.

I suppose we are getting used to such
Taiwanese English as “When finished
the measurement Switch OFF the
battery” and “As battery power is not
sufficient LCD will display ‘BT’ Re¬
placement with one new batterie type
9V is required”.

Although these deficiencies do not
detract from the operation of the two
meters, it would be very pleasant if they
could be corrected.

The prices for the TES-2360 DMM
(Jaycar catalog No. QM-1475) is $169,
and for the WFC-308 (QT-2330) is
$299. Both meters are available from
Jaycar stores. (P.M.) ❖

ELECTRONICS Australia, October 1992

141

Solid State Update

KEEPING YOU INFORMED ON THE LATEST DEVELOPMENTS IN SEMICONDUCTOR TECHNOLOGY

) XCP92514Z

* uuuuLiuuumj '

■■■■■■

wmmmmmmammamm

Wide bandwidth op-amp

A new wide bandwidth, current-feed¬
back operational amplifier, model 623, is
now available from Burr-Brown.

The new part has a small and large sig¬
nal bandwidth of 280MHz, an output cur¬
rent capability of +/-70mA and a
slew-rate of 2000V/us.

Along with other equally impressive
parameters, these make the OPA-623 very
suitable for application in high-resolution
video. RF and IF circuits and in com¬
munications equipment. It is also avail¬
able as a photomultiplier tube
preamplifier.

The new circuit design and process
achieves performance that is unattainable
with monolithic IC technology. It in¬
cludes, however, a monolithic integrated
current-feedback amplifier. It provides
280MHz large-signal bandwidth at +/-
2.5 V output level, as well as the 2000V/us
slew rate.

For further information circle 273 on
the reader service coupon or contact
Kenelec, 48 Henderson Road, Clayton
3168; phone (03) 5601011.

IF amp chip

Avantek, a subsidiary of Hewlett-Pack¬
ard, has introduced a TO-8 packaged
amplifier combining high reverse isola¬
tion with relatively low gain, operating in
the 10 to 1500MHz intermediate-frequen¬
cy range.

This combination of performance and
dynamic range of receivers in com¬
munications, electronic defence,
electronic intelligence and radar systems.

The design of this new amplifier is free
of ferrite couplers or transformers, and
exhibits typical performance of 11.5dB
gain with 50dB of reverse isolation (at
+25°C), and good efficiency over a 10 to
1500MHz bandwidth.

Designated UTO-1576, the amplifier’s
high reverse isolation with moderate gain
makes it particularly suitable for use in
pre-amplification and post -amplification
for passive mixers—as a buffer for oscil¬
lators, switches or filters and as a general-
purpose IF or RF amplifier.

Used as an RF amplifier, the UTO-1576
can help improve the suppression of
radiated LO signal at the antenna.

Guaranteed performance features of the
UTO-1576 amplifier include 10.5dB
small-signal with 0.5dB gain flatness,
5.0dB noise figure, +9dBm output power
(ldB gain compression) and 40dB reverse
isolation, over the 0 to +50°C temperature
range. Performance is specified over the
full -55 to +85°C temperature range.

Also available is the UTC-1576, which
is the same amplifier packaged in a 25 x
21 x 13mm aluminium case, equipped
with RF connectors and RFI-filtered DC
feedthrough.

For further information circle 279 on
the reader service coupon or contact VSI
Promark Electronics, 16 Dickson Avenue,
Artarmon 2064; phone (02) 439 4655.

Fast EPROM programmers

The HEP Series of 8Mb EPROM
Programmers is aimed at the mass
production high speed market of EPROM
programming.

The HEP-808 can program EPROMs
from 2716 to 278000, including page¬
mode EPROMs and EEPROMs, to
28256A’s. It has eight sockets, extra

2Mb BIOS chip

In response to the growing size of the BIOS (basic input/output
system) code required to support today’s advanced desktop and
mobile computers, Intel Australia has extended its Boot Block
flash memory product line to include both a 2Mb and a 4Mb
device. Flash memory’s nonvolatility and read/write
functionality allows PC BIOS to be upgraded quickly and easily
without losing critical system boot code.

Available in user-configurable x8 and xl6 architectures for op¬
timum system design, the new 2Mb 28F200BX/002BX and 4Mb
28F400BX/004BX feature 60ns access times, allowing zero
wait-state performance with many of today’s highest perfor¬
mance microprocessors, such as the 25MHz Intel386TMSL.

The 28F200BX/002BX Boot Block architecture features one
lockable 16KB boot block to securely store the basic boot code
required to initialise the host system, eliminating the possibility
of inadvertent erasure; two 8KB parameter blocks for storing
product codes, setup parameters or system diagnostics; and two
main blocks of 96KB and 128KB each for storing ROM-ex¬
ecutable programs such as MS-DOS, specialised video drivers,
basic and advanced power management (APM), and card and
socket service utilities. The 4MB 28F400BX/004BX is similarly
configured, but adds two 128KB main blocks.

To reduce system-level power consumption and extend the
battery life to today’s mobile PCs, the two new devices feature a
deep powerdown mode (0.2uA typical), low active and standby
power requirements (25mA and 0.1mA, respectively), plus a
new automated power saving feature that allows the chip to shift

142 ELECTRONICS Australia, October 1992

into a 0.8mA static mode between reads. Each is also available in
3.3V read versions.

The new chips, manufactured on Intel’s 0.8um ETOX-HI
process technology, are available in 60, 70 and 80ns access
speed versions.

For further information ciiefe 271 on the reader service
coupon or contact Intel Australia, PO Box 1486, Dee Why 2099;
phone (02) 975 3300.

Fast 24-bit VGA controller chip

Cirrus Logic has introduced its TrueColor VGA’ family of
four pin-compatible, single-chip graphics controllers which
combine 16 and 24-bit colour industry-standard VGA and
SuperVGA compatibility, and graphical user interface (GUI)
acceleration.

The TrueColor VGA family is claimed as the first pin-com¬
patible set of graphics controllers to offer a seamless upgrade
path from accelerated SuperVGA to cost effective 24-bit, or
‘true-colour’ solutions. This provides designers of desktop com¬
puter systems and add-in boards a line of products spanning the
complete range of features necessary to support users of
Microsoft Windows and the growing market for true-colour
applications.

The family of products includes the CL-GD5420 SuperVGA
controller, the CL-GD5422 VGA controller (which adds 16 and
24-bit colour capabilities to the 5422’s feature set), the CL-
GD5424 local bus VGA accelerator and the CL-GD5426 VGA
GUI accelerator. All devices feature on chip R AMDACs and fre¬
quency synthesisers, allowing even a complete subsystem with
full GUI acceleration and 24-bit (16.8 million) colour capability
to be implemented using a single chip and as few as two standard

DRAMs. The family supports the entire VGA and SuperVGA
resolution range from 640 x 480 pixels to 1280 x 1024 pixels, as
well as dot clock rates of up to 80MHz.

For further information circle 275 on the reader service
coupon or contact Cirrus Logic, 3100 West Warren Avenue,
Fremont CA 94538 USA; phone (510) 623 8300.

operation keys, and menu window-
driven software.

This software allows file loading,
saving, full screen editing for binary and
ASCII data, blanking, checking, reading
programs, verifying and auto use. The
chip is capable of programming eight
27256’s in 20 seconds.

The 808 can be connected with the
TCU-500, a controlling unit to become a
stand-alone, high-speed programmer with
no connections needed to the PC/XT/386.

For further information circle 278 on
the reader service coupon or contact Bal-
tec Systems, PO Box 107, Paddington
4064; phone (07) 369 5900.

32-bit RISC chip
for portables

VLSI Technology has introduced the
newest member of its ARM (Advanced
RISC Machine) 32-bit RISC micro¬
processor family, the ARM610.

Targetted for cost effective, battery
operated systems such as the recently an¬
nounced Apple Computer ‘Newton’ fami¬
ly of Personal Digital Assistants, the 610
is claimed to give the highest perfor-
mance-per-watt in the industry, offering
29k Dhrystones at 25MHz, with a dis¬
sipation of less than 600 milliwatts.
Availability in the new Thin Quad Flat
Pack (TQFP) package allows the 710 to
be used in applications where space is at a
premium.

The ARM610 consists of a 32-bit RISC
processor, a memory management unit
(MMU), 4KB of cache memory, write
buffer, and full boundary scan circuitry,
and offers low power consumption (4.5
milliamperes/MHz). It is fully supported
by software development systems that run

Discontinued ICs

Due to declining usage as the market
has moved to more up to date tech¬
nologies, Philips Components has

decided to discontinue certain lines.

The product families to be discon¬
tinued are:

• 74XXX TYL logic,

• 74LSXXX low power TTL logic,

• 74SXXX Schottky TTL logic,

• 10K ECL, and

• 74AC/ACTX CMOS logic.

Philips says it will concentrate its
resources on the HEF4000,

PC74HC/HCTXX, 100K, N74FXX,

on Sun, DOS, and Macintosh operating
systems, enabling fast and efficient code
compilation.

For further information circle 276 on
the reader service coupon or contact
VLSI Technology’s Inquiries Dept, 134,
200 Parkside Drive, San Fernando, Calif.,
91340; phone (408) 434 7905. (Quote ref¬
erence code ARM610).

74ABTXX, Futurebus, Multibyte, and
74HLL33XXX logic families.

For further information contact Philips
Components, PO Box 373, North Ryde
2113; phone (02) 805 4455.

Power suply monitor

Maxim’s MAX690A/MAX692A
microprocessor (uP) supervisory circuits
reduce the complexity and number of
components required to monitor power
supply and battery functions in
microprocessor systems.

The functions include power-on reset,
battery back-up switchover, power-fail or
low battery warning, and programmable
watchdog timer.

Guaranteed RESET assertion at Vcc =
IV prevents faulty microprocessor opera¬
tion at low power supply voltages, while
low supply currents (luA maximum in
back-up mode and 350uA maximum in
operating mode) conserve system powe
and extend battery life.

The chips include a precise threshold
detector and 140ms timer to generate a
high quality reset signal under all condi¬
tions of power-up, power-down, momen¬
tary power interruptions, and brownouts.

The MAX690A threshold detector
trips at 4.65V for 5% power supplies,
while the MAX692A trips at 4.4V for
10% supplies.

Applications include low-power con¬
trollers, intelligent instruments, and any
uP or uC system that requires accurate
power supply monitoring and battery
switchover.

For further information circle 272 on
the reader service coupon or contact Vel-
tek, 18 Harker Street, Burwood 3125;
phone (03) 808 7511. ❖

ELECTRONICS Australia, October 1992

143

Software Product Review:

DSP'S DADiSP 3.0
GRAPHICS WORKSHEET

Wouldn’t it be nice if scientists and engineers had a package like a more sophisticated form of the
spreadsheets used by accountants and managers, which could quickly and easily process, ‘boil
down’ and plot their experimental/testing data in graphical form? They do, as it happens. It’s called
DADiSP, and it can perform all manner of impressive tricks.

by JIM ROWE

One of the biggest chores in many
areas of science and engineering is to
‘boil down’ raw experimental or meas¬
urement data, into a meaningful form —
where you can see what all that data
means , and discover the underlying
trends. Generally this means getting it
into graphical form, because we humans
find this form the most easily and quick¬
ly digested.

Back in the ‘BC’ era (before com¬
puters) this was all done by tedious
manual calculation, tabulation and plot¬
ting; but when calculators and com¬
puters came on the scene, these were
soon delegated to do the number-
crunching hackwork. It was much the
same in accounting.

Of course for a long time, computers
were not much good at anything other
than sheer number crunching. For quite
a while you even had to write a new pro¬
gram, each time you wanted them to per¬
form a new kind of crunching job — but
this changed with the evolution of
electronic spreadsheets, which provided
the ability to perform quite powerful
data manipulation and tabulation,
without the need for programming in the
traditional sense.

Soon spreadsheets were also able
to plot and graph the processed data,
too — simplifying even the last phase of
data reduction, at least for accountants
and managers.

But scientists and engineers were still
left with many of their needs unmet, be¬
cause until recently spreadsheets could
only perform relative unsophisticated
maths: addition, subtraction, multiplica¬
tion, division, totalling and so on.
They’ve been little more than the
equivalent of the four-function cal¬
culator, in data reduction terms.

If you wanted to perform thing s
like a fast Fourier transform (FFT),
or a time integral or differential, or
fancy statistics, or matrix manipulation,
or exponentiate, or plot a 3-D or 4-D
graph, you’ve generally been on your
own. It was largely back to writing
custom programs...

Enter a US firm called DSP Develop¬
ment Corporation, with its DADiSP
package (pronounced day-disp) — an
‘interactive graphics worksheet’
designed especially for scientists, en¬
gineers and other technical people.

DADiSP is essentially a graphically-
orientated development from, and en¬
hancement of, the electronic
spreadsheet And at the same time it’s
designed specifically for the manage¬
ment, analysis, reduction, transforma¬
tion and display of technical data. In
place of the spreadsheet’s ‘cells’, it sub¬
stitutes graphical windows, each of
which can display either raw or derived
data in a multiplicity of forms.

Inside, the package there’s a huge
library of processing functions,
able to perform anything from simple
maths to very sophisticated functions,
and then plot the results in virtually any
desired form.

And the key to DADiSP’s appeal is
that you don’t need a PhD in advanced
maths to drive all of these high-powered
data reduction, manipulation and display
tools. Just as you can drive a spreadsheet
by simply keying in simple expressions,
and indicating the cells whose contents
are to be manipulated, DADiSP lets you
call up its functions and facilities in
much the same way.

You simply indicate the window in
which the result is to appear, the window
or other source which is to provide the

data to be used, and then select the
desired analysis functions from its pop¬
up menues.

Then the result simply appears —
generally within a few seconds. Change
the data in the source window, and the
display in the derived window or win¬
dows changes to match; it’s just like a
spreadsheet, where the result of any
change ‘ripples down’ to the result at
the bottom...

Just as with a spreadsheet, DADiSP
also lets you print out your results, in
this case in high quality graphical form.
And you can save a complete worksheet
on disk, ready to be used again at a later
stage, with new data.

You can get the data into DADiSP in
two broad ways: as a computer file, or
directly from an instrument or measur¬
ing system hooked up to your computer
via the IEEE-488 (GPIB) bus.

The package will ‘import’ disk file
data in a variety of forms, including
ASCH, Lotus PRN, byte-wide, 16-bit in¬
teger, IEEE 32-bit floating point or IEEE
64-bit double precision formats, and it
can also ‘export’ processed data in any
of the same formats.

Importing of data directly from IEEE-
488 based instruments is performed
using an optional accessory package,
called DADiSP-488, which allows
convenient menu-driven control of
the instruments, and transfer of data
from them.

A different accessory package called
DADiSP/LT performs the same broad
functions with many of the popular A-D
data acquisition boards.

When it comes to DADiSP’s data
manipulation and reduction functions,
there are literally too many to even list
here. Even the basic package seems to

144

ELECTRONICS Australia, October 1992

have well over 200, ranging from maths
and statistical functions through type
conversion, trig and hyperbolic func¬
tions to matrix functions, series genera¬
tion, peak analysis and transformation.

In the last of these areas alone there’s
five kinds of FFT (including 2-D), DFT,
auto-and cross-correlation, convolution
and 2-D convolution, Hamming, Han¬
ning and Kaiser windowing, spectrum
and power spectral density.

Yet another DADiSP optional acces¬
sory package called DADiSP/Filters al¬
lows you to design and use both FIR
(finite impulse response) and DR (in¬
finite input response) filter functions.

For display of both raw and processed
data, DADiSP provides options of a line
graph, a scatter plot, stick or bar charts, a
waterfall plot, a 3-D plot, a 4-D
‘colourisation’ or a basic table of num¬
bers. You can also scroll, expand or
compress the data in any direction, zoom
in on a region of interest, add grids, ad¬
just the scaling law, overlay multiple
graphs, adjust the colours and so on.

By the way, a single DADiSP
worksheet can contain up to 100 dif¬
ferent windows, each with raw or
derived/transformed data.

The more windows you have the
smaller they become in their basic form
arrayed on the screen, but you can al¬
ways zoom any window up to full screen
to examine its content in detail. When

the windows are printed out they are
each blown up to full page size, as well.

DADiSP is compatible with a variety
of printers, from Epson and compatible
dot-matrix types, through Oki
Microline, Panasonic and Toshiba 24-
pin models to HP Thinkjet, Paintjet and
LaserJets and compatible lasers. At
present it doesn’t seem to be able to
drive a PostScript printer directly, but it
can direct PS output to a disk file for
printing via another package.

System requirements

There are X-Windows versions of
DADiSP for high-end workstations such
as those of Sun, HP, IBM, DEC, NeXT,
Concurrent and others.

However there is also a version
which runs on IBM-compatible PCs,
which runs under DOS 3.0 or later and
uses its own windowing user interface.
This version is able to address up to
16MB of RAM.

The PC version needs a 286, 386 or
486 processor, with a 287 or 387 floating
point co-processor recommended for
286 and 386 systems to enhance
processing speed. It requires 640k of
conventional memory and at least 2MB
of extended memory.

It does not use expanded (EMS)
memory, and in fact is incompatible with
many EMS memory managers.

It can work with virtually any of the

standard video display cards, although
an EGA, VGA or Hercules card will
naturally give rather better display
resolution. The package also needs
about 2.5MB of free disk space for in¬
stallation on a hard disk — which is
again desirable, to speed up operation.

By the way, DADiSP is protected
using a hardware ‘dongle’, which must
be plugged into the computer’s printer
port before the package will run.

This is both protection against un¬
authorised distribution, and to ensure
that only one copy of an authorised user
copy can be in use at any one time.

Trying it out

A sample copy of DADiSP 3.0, the
latest version of the package for the PC,
was kindly sent to our office by DSP’s
Australian distributor Interworld
Electronics and Computer Industries, so
we could try it for ourselves.

We installed it on a 486-based
machine running at 33MHz, with 3MB
of extended memory and an S-VGA
graphics adaptor, running DOS 5.0. The
installation itself didn’t present any
problems, although it took rather longer
than we expected.

As part of the initial configuration
we found that the package doesn’t seem
to be able to take advantage of the S-
VGA enhanced resolution modes; the
highest option is essentially standard

ELECTRONICS Australia, October 1992

145

DSP’s DADiSP3.0 Graphics Worksheet

Mi;

6.16 e. 13

>.36 6.33 6.46 6.45

M; S»tfllnm^yl >

M oiiTe~

B.e _ i6ae.e

Reduced to less than 30% of their actual size, here are four window print-outs
from DADiSP 3.0. W1 at top left shows a digitised sample of speech, while
W2 at top right shows the spectrum plot derived from W1 by DADiSP. W3 at
lower left shows the first 75ms of the W1 sample, and finally W4 shows the
spectrum plot of this smaller sample.

1266.6 1666.6

VGA. In the absence of direct PS print¬
ing we also set it up to print in HP Laser-
jet II mode, and set up our dual-mode
laser accordingly.

The computer concerned is normally
set up with XMS and EMS memory
managers, to provide both 3MB of ex¬
panded memory as well as the same
amount of extended memory. This
generally works out well, allowing a
wide variety of software to have suffi¬
cient memory for its needs.

And DADiSP seemed quite happy
with this setup when we fired it up im¬
mediately after installation; it was only
when we tried running it again the next
day, that it refused to run — throwing up
mysterious error messages, which
weren’t explained in the manuals
(Murphy’s law!).

It was after studying the
‘Troubleshooting Tips’ section at the
rear of the User Manual that we dis¬
covered that DADiSP really doesn’t like
to share its computer with virtually any
memory managers — especially any
kind of EMS manager.

Not a very friendly package, it seems
— you have to use a different
AUTOEXEC.BAT and CONFIG.SYS
combination, if you normally run such
managers, so that DADiSP can have the
hardware all to itself...

Still, when it is running, it is a
very impressive package indeed. The
ability to derive transformed and
reduced versions of data, quickly and
directly in graphical form, makes it ex¬
tremely powerful.

Just as an example, I set up four win¬
dows Wl-4. Into W1 I fed a ‘raw’ data
sample — which happened to be a
sample of digitised speech (‘Chicken
Little’), supplied as part of DADiSP’s
built-in demo/tutorial.

Then I told DADiSP that in W2, I
wanted to see a plot of the frequency
components in the W1 sample — i.e., a
spectrum plot.

This was done very simply with the
mouse, by selecting window W2, calling
up the appropriate menu, selecting the
spectrum plot function and finally
typing in ‘Wl’ as the source of data for
the function.

Within a second at most, the spectrum
plot appeared in the W2 window of the
diagram — showing a main peak at
about 500Hz, lesser peaks at about
180Hz and 350Hz, and a reasonable
amount of ‘noise’.

Then I told it that in W3,1 wanted to
see an expanded version of the first

75ms of the signal in Wl, to examine the
first ‘burst’ of speech in greater detail.
This appeared almost immediately, the
moment I made the final click with the
mouse button.

Finally, I called for another spectrum
plot in W4, this time from the smaller
speech sample in W3. As before this ap¬
peared within a second, and as expected
the plot of this smaller sample was
similar to the first, but with lower
resolution and less ‘noise’.

The four windows of this example are
shown in the diagram, as printed out via
the laser printer. As printed each one is
almost A4 size.

Other functions turned out to be
equally easy, and to operate with the
same impressive speeds. Presumably
this was partly because I was using a
486/33MHz machine, but even on 286
and 386 machines I gather it’s still
reasonably speedy — as long as you’re
running a co-processor.

In short, then, my impression of
DADiSP in operation is that it’s an ex¬

tremely powerful tool for the analysis,
reduction and presentation of technical
data. Yet at the same time it’s surprising¬
ly easy to use.

The combination of these two impor¬
tant qualities should make it of enor¬
mous value to scientists, engineers and
anyone else who needs to work with
technical data.

My only gripes are that it would be
nice if DADiSP could print directly to a
PostScript printer, and if it wasn’t quite
so finicky about sharing the computer
with memory managers. But perhaps
these things are part of the price we pay,
for DADiSP’s power and speed...

Talking about prices, the version of
DADiSP 3.0 which runs on IBM com¬
patible PCs is priced at $2765 plus P&P
where applicable.

Further information on the package is
available from Interworld Electronics
and Computer Industries (Aust.), 1G
Eskay Road, Oakleigh South 3167 (PO
Box 300, Bentleigh 3204); phone (03)
563 7066. ❖

146

ELECTRONICS Australia, October 1992

READER INFO NO. 36 READER INFO NO. 35

PC DIAGNOSTICS MADE EASY

SLASH DOWNTIME AND
OPERATING PROBLEMS

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PCs that don’t issue POST codes. KickStart 2 tests your
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HARD CORE TESTING FOR
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partition editor allows you to set up multiple partitions;
back-up program transfers hard disk image on
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Ideal for UNIX and other operating systems, the self¬
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Silicon Valley

NEWSLETTER

Apple’s Claris software development subsidiary is housed in this imaginative
building, which features outdoor garden areas on two of the upper floors. The
group will be developing software packages for Apple’s new ‘Newton’ and
‘Sweet Pea’ Personal Digital Assistant (PDA)products.

Apple & Toshiba in
PDA venture

Apple Computer is teaming up with
Toshiba to develop jointly a second type
of Personal Digital Assistant (PDA)
device, which will run under advanced
new multimedia operating software being
developed by the Kaleida joint venture
between Apple and IBM.

The so-called ‘Sweet Pea’ system will
be handheld, and run programs and data
stored on optical disks. It will cost under
US$1000 when it is introduced around
the middle of next year.

The announcement comes less than a
month after Apple announced the New¬
ton, a handheld PDA that is being
developed in cooperation with Sharp
Electronics. While the Newton will be
aimed at business executives, travelling
salesmen and other professionals, Sweet
Pea will be targeted at consumer and
educational markets.

While not releasing any details of the
device, Apple chief John Sculley said
during a speech before the Digital World
conference in Beverley Hills that Sweet
Pea will be the first product to run
under a version of the ‘Script X’ multi-
media operating system being developed
at Kaleida.

Sculley also said that Apple, in an effort
to set the standard for multimedia PDA’s
will probably licence portions of Script X
to other companies that want to develop
other PDA’s. This would help Apple push
Script X as an industry standard, which
in return would cause more application
companies to develop programs for Script
X-based PDA’s.

Already, Sculley said, three com¬
panies — including two of the world’s
largest entertainment companies, Time
Warner and Paramount — have com¬
mitted themselves to developing titles
for Sweet Pea. Apple’s Claris software
group will also develop a number of ini¬
tial applications.

In his speech, Sculley explained Apple
needs to team up with major Japanese
electronics companies and licence them
critical technology because the cost of
developing the PDA market is too
prohibitive for Apple alone. “We can’t
drive down the cost of these PDA’s

without the know-how of companies like
Sharp and Toshiba.”

IBM, Toshiba
to team up on Flash

In a move that could shake the founda¬
tions of the Intel-dominated Flash
memory market, IBM is entering a joint
venture with Japan’s Toshiba to develop
new generations of Flash chips — which
both companies would incorporate into
their own computer products, as well as
sell on the open market

The teaming of IBM and Toshiba could
have major implications for the Flash
market. Both companies are already at
the leading edge of DRAM memory
chip design and development. If they are
able to transfer their design and manufac¬
turing expertise in DRAMs to the Rash
market, Intel would face two new for¬
midable competitors.

For IBM, a major commitment towards
Rash also signals an internal determina¬
tion that solid state memories, in the
long run, will be the memory vehicle of
choice for a number of key product lines
— perhaps even desktop PCs. For
Toshiba, a jump into the still small Rash
market could give the company a head
start when the Rash business takes off in
a big way — which is expected during the
second half of this decade.

Toshiba, like most Japanese DRAM
makers, is frantically looking for ways

to leverage their high-density DRAM
manufacturing technology into other
more profitable product lines. Flash
memories, which still command very
high prices per million bits of chip
capacity, are a natural field for the
Japanese to explore.

Dataquest in San Jose predicts that
Rash memories will turn into a US$1.5
billion market in the next three years, up
from just US$130 million in 1991.

Ironically, it was Toshiba which
developed the first Rash memories, in the
mid-1980s. But the company, too busy
trying to become the dominant DRAM
supplier, failed to make Rash memories a
high priority. That allowed several
American firms, most notably Intel,
Xicor, and Seeq to acquire a vast majority
of the Rash market.

Interactive TV system
to go nationwide

Hewlett-Packard’s ‘Interactive Net¬
work’ TV play-along system is selling so
well during its first couple of months that
the system’s parent firm has announced
plans for a national US sales program.

Until now, the IN console, which lets
consumers interact with live television
programs via a video game like console,
has only been available in California.

While HP is producing the console the
network is being operated by Interactive
Network. Company president David

148

ELECTRONICS Australia, October 1992

Lockton said his firm has received new
venture capital that will allow it to offer
the system on a nation wide basis.

The IN system receives digital data
transmitted over unused portions of local
FM radio stations. The signals are
synchronised with TV broadcast signals.
Viewers, watching a game show, can
answer questions being asked of the
game’s contestants and the system will
show how well they did.

TV education programs could be
revolutionised with this online interactive
capability. Eventually, viewers may be
able to win prizes as the system’s central
computer will be able to track the scores
of individual viewers.

When the system was launched earlier
this year, IN and HP said they hoped to be
able to sell a million units in its first year.
IN’s Lockton said sales so far are well
ahead of this schedule.

Japan’s new chip
agreement may fail

Too few American semiconductor
vendors are making the kinds of chips
that Japanese buyers need most and for
that reason it will be difficult for Japan to
allow foreign marketshare to increase
quickly, according to Nobuo Kanoi,
chairman of the Foreign Semiconductor
Committee of the Electronics Industry
Association of Japan (EIAJ).

The statement is the first public in¬
dication that Japan may not be able to im¬
plement the terms of the emergency
agreement the EIAJ signed recently. That
agreement was aimed at quickly boosting
the foreign share of the US$20 billion
Japanese chip market from its current
stagnant 14% level to around 20%, as it
is supposed to by the end of this year
under the US-Japanese Chip Trade
Agreement of 1991. Kanoi made his com¬
ments in response to President Bush’s
warning to Prime Minister Kiichi
Miyazawa that Japan must do more to im¬
prove foreign access to its automotive and
semiconductor markets.

Kanoi said Japanese electronics com¬
panies are doing their best to buy more
foreign semiconductors. But they are also
confronted with a severe recession and
they must spread the economic hardship
among all of their suppliers: “Japan
doesn’t treat others badly, while treating
itself well.”

One of the reasons progress in market
share will be slow, he explained, is that
many semiconductors usal by Japan’s
electronics industry are application
specific, and it takes time to work with
new vendors to develop such chips.

“The problem is that there are very few

American companies that can supply ex¬
actly what customers need here,” Kanoi
said. He added that while Japanese com¬
panies can buy more American stand¬
ardised parts, this represents only a small
part of the market. “Even if the inside of a
chip is identical, if the packaging or
dimensions are different, we can’t use it”

At the Semiconductor Industry As¬
sociation office in San Jose, spokes¬
woman Angela Newlove disputed
Kanoi’s statements.

“A year ago, we signed an agreement
with the Japanese government and they
determined that we have the products that
they could use, and they agreed the 20%
market share was achievable. The joint
statement we signed with the EIAJ was to
implement an emeigency measure to try
to achieve this 20% share. Here we are
one month later and Kanoi is talking
about why it won’t succeed, instead of
how he plans to make it succeed.”

Intel invests in
VLSI Technology

In a move designed to bring Intel chips
into the potentially huge market of
products that blend traditional consumer
electronics with advanced computer tech¬
nology, Intel announced it has agreed to
buy a 20% equity position in San Jose
chip maker VLSI Technology. As part of
the deal, the Santa Clara chip maker will
allow VLSI to develop and manufacture
new versions of its low power 386SL
processor.

The deal means a major strategic shift
for Intel. Since it terminated its technol¬
ogy exchange agreement with AMD in
1987, Intel has tried hard to remain the
sole source for its line of X86 processors.
Recently, AMD, Cyrix, Chips & Technol¬
ogy and Texas Instruments have brought
competing clones of the 386 and 486
chips to market.

In addition to receiving US$50 million
in cash from Intel in return for 20% of its
stock, VLSI will now be allowed to make
low power versions of the Intel 386SL —
chips designed for a new generation of
handheld devices such as PDA’s. Already
VLSI is producing a low power RISC
processor for Apple Computer’s new
family of PDA’s.

Intel wants to ensure its processors will
play a signficant role in the PDA market.
Intel itself may not be interested in
producing the PDA chips, which will be
high volume, low price in nature, and
often require considerable customisation.

But at the same time, Intel does not
want to see all of the PDA business end
up in the hands of its competitors,
such as AMD and Texas Instruments.

Taking an interest in VLSI will ensure
Intel an indirect role in the market for
PDA processors.

Intel said it chose VLSI because of that
company’s strength in the area of cus¬
tomisable chips and its expertise in low
power consuming components.

VLSI said it will use some of the Intel
money to expand its Texas-based
manufacturing facilities.

Intel delays 586 launch

Intel is delaying the launch of its next
generation P-5 (586) microprocessor, in
an effort to avoid the same embarrass¬
ment the company suffered with bugs that
surfaced following the launch of the pre¬
vious 386 and 486 processors. Originally
scheduled for this fall, Intel said it now
expects the P-5 to debut in the first
quarter of 1993.

Industry analysts said there may have
been additional motives to the delay. Be¬
sides giving engineers more time to get
rid of any remaining bugs, the delay
will give Intel the opportunity to use fab
lines in Oregon and New Mexico that
were reserved for P-5 volume produc¬
tion, to produce more of Intel’s best sell¬
ing 486 chips.

The decision to delay the P-5 was also
aided by the recent court victory over
AMD, which is keeping a major com¬
petitor out of the 486 market. The ab¬
sence of AMD and its ability to produce
high volumes of 486 chips will keep
486 prices at a stable and profitable
level. Even Cyrix, which recently entered
the 486 market, is unlikely to unleash a
price war as long as its sales continue to
meet targets.

The only drawback for Intel is that
the delay may hurt the company’s
strategy of pitting the P-5 against SPARC
and MIPS RISC processors in the
workstation arena. Intel has said it is con¬
fident that the 66MHz P-5, which con¬
tains some three million transistors, will
be able to compete effectively in the
workstation market

H-P wins huge
workstation order

Hewlett-Packard has been awarded one
of the largest single contracts in worksta¬
tion history, as the German Bundespost’s
Telekom division has signed a purchase
agreement worth US$125 million for
HP’s line of workstations and printers.

The equipment will be delivered over
the next several years. It is part of a major
technology restructuring program under¬
way at the German Bundespost whose
Telekom unit is Europe’s largest telecom¬
munications carrier. ♦>

ELECTRONICS Australia, October 1992

149

Computer News
and New Products

Low cost PCB software

Easy-PC is a PCB and schematic diagram design program
which produces professional quality output, but costs only $249.

The package has the power to handle multilayer boards with
up to eight conductor layers, plus top and bottom silk screens
and solder resists. It allows 128 different track widths and
pad sizes to be used, from 0.002 to over 0.5" with full surface
mount support.

Schematic diagrams can be quickly created in an identical
manner to the PCBs, while check plots and artworks can be
produced on dot matrix printers, pen plotters or laser printers,
and Gerber files can be generated for photo plotting.

Two additional libraries are also available: library 1, a collec¬
tion of over 1000 schematic drawing symbols covering 13 logic
families, including microprocessors, memories and support
chips; and library 2 which contains over 500 surface mount com¬
ponent land patterns for passive devices, DELs, quads, flatpacks,
chip carriers and PLCCs.

Easy-Link now also has a file translator which allows Gerber
files from older PCB design programs to be translated into Easy-
PC’s format.

For further information circle 166 on the reader service
coupon or contact Plunkett Industrial Electronics, 21 Blacks
Road, Gilles Plains 5086; phone (08) 261 3799.

Customised DA cards

The PCL-814 represents a new generation of modular PC-
compatible Data Acquisition Cards. The cards* task-orientated
design offers the user greater flexibility when customising their
data acquisition system. This is achieved by plugging in only the
modules that are required for the application.

The card comes equipped with a 14-bit resolution 100kHz
high performance A/D module, which provides 16 channels of
differential analog signal measurements. But the special feature
of the PCL-814 is that it has two 64-pin ‘piggy-back’ connectors
for function expansion, using plug-in modules. There are cur¬
rently three different I/O plug-in modules available, the PCL-
814-DA-1, PCL-814-TC-1 and the PCL-814-DIO-1.

The PCL-814-DA-1 modules provides two channels of 12-bit
D/A output. Each channel can be individually configured for
voltage or 4-20mA current loop. The PCL-814-TC-l is a general
purpose counter/timer module with an on-board 1MHz crystal
timebase — the module uses an AMD 9613 counter timer chip to
provide five channels of 16-bit up/down counters. The PCL-814-
DIO-1 module is equipped with an 8255 PP1 chip to provide 24
bit digital input/output configuration.

For further information circle 163 on the reader service

coupon or contact Priority Electronics, 23-25 Melrose Street,
Sandringham 3191; phone (03) 521 0266.

MAESTRO PTY LTD

A FULLY FEATURED HIGH SPEED MODEM IS NOW AVAILABLE

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READER INFO NO. 32

Remote operation software

Neutrik’s new AS03 Software allows
full remote operation of its A Series Audio
Test Instruments, including the A1
Audio Test & Measurement System.
Designed to run on IBM XT, AT and
compatible computers, the AS03 provides
enhanced measurement functions for the
A1 audio test set.

Employing full bidirectional com¬
munication, the AS03 package provides
complete control of all A1 functions. It
features a window-controlled user inter¬
face with mouse support and on-line help
for ease of operation.

AS03 expands the capability of the A1
Audio Test System with enhanced meas¬
urement functions, including: fixed range
measurements, amplitude sweeps, time
sweeps, table sweeps, external sweeps
(frequency and level), tolerance curves,
calculation of tolerances and a tolerance

comparison function. It can simultaneous¬
ly display several response curves on
screen for comparison, as well as load and
save graphics and tables to disk. The
package is supplied with a wide selection
of printer and plotter drivers.

For further information circle 162 on
the reader service coupon or contact
Amber Technology, Unit B, 5 Skyline
Place, Frenchs Forest 2086; phone (02)
975 1211.

All electronic parts are fully protected
by O-ring seals, yet the 5cm diameter ball
can easily be removed for ease of clean¬
ing without compromising water-proof
integrity. The ball movement is trans¬
mitted to the encoders via a novel drive
mechanism. Resolution is 800 edges per
ball revolution.

On the panel-mount version, the full
range of interface options are available,
including RS232 or TTL data stream. It
supports most computer hardware, in¬
cluding IBM PC/AT, PS2 and RS6000,
DEC Workstations 3100, VSV212 and
VT240, Sun Microstations and Silicon
Graphics cards. Mouse Systems,
Microsoft and Summagraphics (bit pad 1
& 2) are all supported as well.

For further information circle 168 on
the reader service coupon or contact
University Paton Instruments, PO Box
402, Riverwood 2210; phone (02) 534
6100.

Low cost programmer

The ChipMaster 3000 is a new low
cost PC/XT/AT or compatible universal
pin-driven programmer from Logical
Devices. Its 40-pin standard ZIF socket
can directly program over 1000 different
devices such as E/EE/PROMs, PALs,
GALs, FPLAs, PEELs, EPLDs, EEPLDs,
and Microcontrollers. SMD devices can
be supported through optional adaptors.

The ChipMaster software allows menu
driven device selection by vendor’s name
and device part number. When a device is
selected, its associated programming al¬
gorithm, voltage and timing parameters
are automatically selected.

The ChipMaster hardware provides two
programmable voltage sources (from 5V
to 25.5V, lOOmV step) to all 40 pins. A
third high current source can be applied to
the specific pin. With these features, the
unit can support all silicon technologies
— NMOS, CMOS, bipolar and ECL.

With the ‘Device Options’ command,
users can edit device programming para¬
meters such as Vpp, Vcc, PW, RETRY,
etc. The unit will display all parameters
using the same names found in vendors’
published data books. With this feature,
you can add new devices (if devices have
the same pin configuration and wave¬
form, but different voltage and timing
specs). This provides an alternative to
waiting for programmer and
manufacturer’s updates.

For further information circle 169 on
the reader services coupon or contact
Emona Instruments, PO Box K720,
Haymarket 2000; phone (02) 519 3933.

Waterproof trackball

For applications in hostile environ¬
ments, Penny & Giles Computer Products
is shipping a new waterproof trackball,
immersible in up to 60cm of water
without tactile feel degradation.

HP printer sharer

ASP has released its ServerJet Si printer
sharer. This product is a card that plugs
into the MIO interface slot of the HP lUsi
(and now HP DesignJet and HP PaintJet
as well) and allows up to seven users to
share the printer.

Maximum flexibility has been a design
goal of the ServerJet Si. Six concurrent
users can communicate with the printer
via serial ports using low cost telephone
jacks. A seventh user has access via a
parallel port, or a second printer can be
attached and addressed with the ASP
software supplied.

If the HP IEsi is required on a network,
it can be connected via the ServerJet Si’s
parallel port, and six non-network con¬
nected users can still simultaneously
share via the serial ports. This is impor¬
tant for network back-up or large file ap¬
plications requiring fast print times.

The software supplied detects which

Micro-Cap IV

more than a circuit simulator.

much more.

For the liberated professional

• IBM OR MAC

DAVID SPALDING PTY LTD

# ,ca77 D&V’tdtptrsoxaMy’ on f 02J 639 3507

45A BLACKETT DRIVE CASTLE HILL NSW 2154

READER INFO NO. 33

ELECTRONICS Australia, October 1992

151

COMPUTER PRODUCTS

HP MIO device it is attached to, either
the HP IllSi, the DesignJet plotter or
the PaintJet XL colour printer. Each port
can then be separately configured, includ¬
ing baud rates to 115.2k baud, auto
emulation sense (PCL and Postscript),
time out and hand shake. The parallel
port can also be set up as either input
or output. Set up is done from an at¬
tached PC or from the control panel of
the HP IHSi itself.

The ServerJet Si comes standard with
1MB of memory but can be upgraded to
4MB for larger files. The ServerJet Si is
the ideal partner for the big HP laser when
a LAN is just not needed. It is priced at
$1551, inc. tax.

For further information circle 167 on
the reader service coupon or contact
Sprinter Products, 22 Darley Road,
Manly 2095; phone (02) 977 8155.

Mac and PC
demo packages

National Instruments Australia an¬
nounces two free demonstration pack¬
ages — one for its popular Lab VIEW
graphical programming software for
the Macintosh, and one for its Lab-
Windows software development system
for DOS PCs.

The LabVIEW 2 Demonstration Pack¬
age summarises the capabilities of
LabVIEW 2, shows the user how to build
a virtual instrument (VI), and examines a
completed VI and its components. The
demo package requires a Macintosh with
at least 2MB of RAM, 2 MB of available
hard disk space, and a 13" monitor.

The LabWindows Demonstration Pro¬
gram gives a comprehensive overview of
the LabWindows 2.1 software develop¬
ment system for programmers using C
and BASIC for data acquisition and in¬
strument control applications.

Sound Galaxy cards

The Sound Galaxy family of multi-
media sound cards has been developed
by Singapore-based Aztech Systems,
and comprises the Sound Galaxy EX,
Sound Galaxy BS and Sound Galaxy
NX cards.

The top of the range Sound Galaxy NX
card incorporates the four major sound
standards of AdLib, Sound Blaster,
Covox Speech Thing and Disney Sound

The demo is based on a functional ver¬
sion of LabWindows, and includes ex¬
ample programs that show how
LabWindows is used to develop applica¬
tion programs.

It requires a PC AT, EISA, or Micro
Channel computer running MS-DOS
(Version 3.0 or later), 2MB of memory, a
minimum 80286 processor, and an EGA
or VGA display adaptor.

For further information circle 171 on
the reader service coupon or contact Na¬
tional Instruments Australia, PO Box 466,
Ringwood 3134; phone (03) 879 9422.

Autodesk supports
Windows NT

Autodesk has confirmed that customers
of its computer-aided (CAD) software
will be able to run AutoCAD on Win-

Source, enabling users to run the largest
library of education, presentation, multi-
media and entertainment software of any
sound card available.

The NX also includes both MIDI and
CD-ROM interfaces, digital input and
output and games ports.

The performance of the NX card is
further boosted by a suite of powerful
and popular software applications and
utilities, including Monologues Speech
to Text Synthesiser, Band-in-a-Box in¬
telligent music accompaniment
software, digital recording and play¬
back utility and other utility software
valued at over $600.

Also included with the Sound Galaxy
NX card is a set of mini speakers which
further enhance the sound quality output

The suggested retail prices (inc. tax),
for the Sound Galaxy cards are: EX $199,
BX $235, and NX $379.

For further information circle 165 on
the reader service coupon or contact
Entcom, 5 Viewtech Place, Rowville
3128; phone (03) 764 3399.

dows NT, a new operating system being
developed by Microsoft Corporation. A
pre-alpha version of AutoCAD for Win¬
dows NT was demonstrated in Chicago
in April.

Autodesk also has restated its intention
to continue investigating extender tech¬
nologies to provide a 32-bit version of
AutoCAD for Windows 3.1, as well as
reaffirming its commitment to new
releases of AutoCAD for DOS.

When available, AutoCAD for Win¬
dows NT is expected to offer all of the
capabilities of AutoCAD on other operat¬
ing systems, as well as take advantage of
the unique capabilities of Windows NT,
including: faster performance, by virtue
of 32-bit architecture; pre-emptive
multitasking; protected mode, stable
operating system; multiple AutoCAD for

Australian Computers & Peripherals from JED... Call for data sheets.

The JED 386SX embeddable single board computer can run with
IDE and floppy disks, or from on-board RAM and PROM disk. It
has Over 80 I/O lines for control tasks as well as standard PC I/O
Drawing only 4 watts, it runs off batteries and hides in sealed
boxes in dusty or hot sites.

It is priced at $999 (25 off) which includes 2 Mbytes of RAM.

JED Microprocessors Ptv. Ltd.

Office 7, 5/7 Chandler Rd., Boronia, Vic. 3155. Phone: (03) 762 3588 Fax: (03) 762 5499

$300 PC PROM

Programmer. x ^(sales tax exempt prices)

Need to programme PROMs from your PC?

This little box simpiy plugs into your PC or Laptop's parallel printer
port and reads, writes and edits PROMs from 64Kb to 8Mb,

It does it quickly without needing any plug in cards.

152

ELECTRONICS Australia, October 1992

READER INFO NO. 26

Windows sessions; and support for multi¬
processor PCs.

For further information circle 170 on
the reader services coupon or contact
Autodesk Australia, 9 Clifton Street,
Richmond 3121; phone (03) 429 9888.

Master Designer 6.0

P-CAD Master Designer 6.0 for DOS is
the latest version of the printed circuit
design package from CADAM, an IBM
company. Version 6.0 now offers a full
32-bit database to handle the most
dense PCB designs and facilitate fraction-
al-thou grids.

It also features a new modem style in¬
terface and design manager that simplifies
the control of projects, together with
software display list graphics for ac¬
celerated screen redraw, automatic
dimensioning and auto-resequencing by
component or grid coordinates.

A new user interface called ‘Prevue’,
uses icons, pop-up windows and pull¬
down menus. Its design manager ensures
consistency between the schematic and
PCB layout — it automatically updates
the PCB and provides full automatic for¬
ward and backward annotation between
the schematic and the layout.

Master Designer 6.0’s 32-bit database
operates with 386 and 486 code for un¬

SIEMENS

limited design capacity. A 0.01-thou
resolution database allows for extremely
fine line design and mixed Im¬
perial/Metric packages, without round¬
off error.

In addition, it is now possible to
have up to 5000 pins per component
and 1000 different pin types. Its Auto-
Dimensioning feature supports simple
to complex geometry, including point-
to-point, datum, centre, diameter,
radius and angular dimensions with
user-controller tolerancing. This allows
easy creation of fabrication and as¬
sembly drawings.

The package is DPMI compatible for
Microsoft Windows, and offers a
VESA driver to support most super VGA
display cards.

An additional feature of the DOS-
based Version 6.0 is that databases and
libraries are compatible with the P-CAD
Unix system, Premier PCB, running on
SUN SPARCstation and the IBM RISC
6000. This enables cost effective net¬
works with a mixture of DOS and Unix
platforms.

For further information circle 173 on
the reader service coupon or contact
Quest International Computer, 1 Hamil¬
ton Place, Mount Waverley 3149; phone
(03)807 7444. ❖

whats

N€UJ

in Speaker Design ?

wn&” 5149 -

Designer

Australia's latest complete
speaker design environment,
includes, enclosure, crossover
& optimisers, zobel, room
placement & much more !

CALSOD 1.20H - $119*#
Australian and powerful

oft ware

New free A . ^ a--*..
eda^ue $ 43-$55 #

LEAP - modular from $449#
LEAP - evaluation $149#
LMS Ver 3.0 - update $195*#

Prices based on AUS$1=US$0.75 _

* demo disk available

# comprehensive data available

ME Technologies

(an ME Sound Pty Ltd subsidiary)

P.O. box 50, Dyers Crossing NSW 2429
« 065 50 2254, fax 065 50 2341

DIN connectors.

Thirty years’ development
makes a big difference.

The big difference between Siemens and
any other maker of DIN connectors is that we
pioneered the field in the early ‘60s.

So we’ve had more experience at designing and
manufacturing them than anyone else.

And as we stock the complete range locally, our
professional support network can supply them to
you in as little time as possible.

Connectors such as our future-proof Sipac
range manufactured to DIN 41642IEL 917
requirements as adopted by several European
Telecom organisations.

Or there are our Siedecon Multi-Point connectors
featuring an added contact row that omits the
irksome alignment of individual connectors.

And finally, our two part DIN 41612 Eurocard
connectors with identical installation
characteristics for mixed configuration in the
one piece of equipment.

Little wonder really Siemens is the largest
components supplier in Australia.

Siemens

Components

Little things make a big difference.

Phone (03) 420 7111 or fax us on (03) 420 7275 for more details.

Ball SIE0106

READER INFO NO. 38

ELECTRONICS Australia, October 1992

153

READER INFO NO. 37

EA DIRECTORY OF SUPPLIERS

Which of our many advertisers are most likely to be able to sell you that special
component, instrument, kit or tool? It’s not always easy to decide, because they can’t
advertise all of their product lines each month. Also some are wholesalers and don’t sell
to the public. The table below is published as a special service to EA readers, as a guide
to the main products sold by our retail advertisers. For address information see the
advertisements in this or other recent issues.

Supplier

State

Altronics

•

Companion Computers

VIC

•

Dick Smith Electronics

ALL

•

Emona Instruments

NSW

•

Geoff Wood Electronics

NSW

•

Jaycar Electronics

Eastern

•

Kalex

VIC

•

Macservice

VIC

•

RCS Radio

NSW

•

Rod Irving Electronics
Scientific Devices

VIC

•

TECS

vre

•

Wagner Electronics

NSW

•

KEY TO CODING:

A Kits and modules
B Tools

C PC boards and supplies

D Components

E IC chips and semiconductors
F Test and measuring instruments
G Reference books

Note that the above list is based on our understanding of the products sold by the firms concerned. If there are any
errors or omissions, please let us know.

Electronics Australia Reader Services

SUBSCRIPTIONS: All subscription en¬
quiries should be directed to: Subscriptions
Department, Federal Publishing Co, PO Box
199, Alexandria 2015; phone (02) 693 9751.
BACK ISSUES: Available only until stocks
are exhausted. Price A$7.50 which includes
postage within Australia only. OVERSEAS
READERS SHOULD ADD A FURTHER
A$2.50 FOR EVERY BACK ISSUE RE¬
QUIRED.

PHOTOSTAT COPIES: When back issues
are exhausted, photocopies of articles can
be supplied. Price $7.50 per project or $15
where a project spreads over several issues.
PCB PATTERNS: High contrast, actual size
transparencies for PCBs and front panels
are available. Price is $5 for boards up to
lOOsq.cm, $10 for larger boards. Please
specify negatives or positives.

PROJECT QUERIES: Advice on projects is
limited to postal correspondence only and to
projects less than five years old. Price $7.50.

Please note that we cannot undertake spe¬
cial research or advise on project modifica¬
tions. Members of our technical staff are
not available to discuss technical problems
by telephone.

OTHER QUERIES: Technical queries out¬
side the scope of ‘Replies by Post', or sub¬
mitted without fee, may be answered in the
‘Information Centre’ pages at the discretion
of the Editor.

PAYMENT: Must be negotiable in Australia
and payable to ‘Electronics Australia’. Send
cheque, money order or credit card number
(American Express, Bankcard, Mastercard
or Visa card), name and address (see form).
ADDRESS: Send all correspondence to:
The Secretary, Electronics Australia, P.O.
Box 199, Alexandria, NSW 2015.

PLEASE NOTE THAT WE ARE UNABLE
TO SUPPLY BACK ISSUES, PHOTO¬
COPIES OR PCB ARTWORK OVER THE
COUNTER.

METHOD OF PAYMENT: (Please circle correct method).

Credit Card:
Cheque:
Money Order:

Mastercard
American Express
Visa

Bankcard

Expiry Date:

Name:.

Address:.

Back Issues:

.Postcode:,

Photostat Copies:.

No.of issues required:.$7.50=.

No.of copies required:.$5.00=.

No.of copies required:...$15.00=.

Total Payment Enclosed $

Signature:.

(Unsigned orders cannot be accepted).

ADVERTISING

INDEX

AEDC..89

Altronics.94-96

Adilam Electronics.OBC

APC Services.65

Auto tron Australia.19

AV-COMM.129

Beaufort Technologies.17

Choice Electric.54

Comma Corporation.89

Companion Computers.107

Computronics.55

Daley Electronics.121

Data Electronics.147

David Spalding.151

Dick Smith Electronics.76-79

EAsubscriptions offer.27

EEM Electronics.121

Elect.Development & Sales.130

Emona Instruments.65

Endeavour Tools.55

Federal Marketing (Books).118-119

Geoff Wood Electronics.25

Heame Marketing Software.11

Hewlett-Packard Aust..26,131

Hycal Electronics.121

Hy-Q International.65

Interworld Electronics.147

Jaycar Electronics.108-111

JED Microprocessors.152

L.E.Chapman.122

Macservice.134-135

Maestro Distributors.150

McGraw-Hill Australia.33

McLean Automation.54

ME Technologies.153

MMT Australia.53

Oadey Electronics.IBC

Obiat..47

Peter Lacey Services.50

RCS Radio.121

Rod Irving Electronics.56-59,100-103

Scientific Devices.55

Seas Speaker Kits.115

Siemens..64,139,153

Technical Applications.130

Technology Circuit Ind.135

Tektronix Australia.IFC

Transformer Rewinds.121

Vintage Wireless Radio Co.106

WES Components.54

Zenology Sales.134

This index is provided as an additional
service. The publisher does not assume
any liability for errors or omissions.

154

ELECTRONICS Australia, October 1992

SECOND GENERATION TUBES/"

We have a limited supply of
some 18mm fibre optically
coupled 2nd generation image
intensifier tubes. These are
ex-military and may have some minor blemishes, but all
produce full gain. With low light lenses these will
produce useful images with as little as starlight
illumination. Can also be IR assisted with IR LED’s or
low power torches, in rare situations where this may be
required. The tubes require a 3V battery and a switch to
make them operational. The viewer illustrated uses one
of these tubes. It was constructed using some low cost
plastic tubing and matching fittings for the case, a
camera lens, and a low cost eyepiece.

Plastic jewellers eyepieces can be used.

FOR THE TUBE Af-

LIGHT MOTION
DETECTOR

Small PCB assembly
based on a ULN2232 1C.
This device has a built in
light detector, filters, timer,
narrow angle lens, and
even a siren driver circuit
that can drive an external
speaker. Will detect
humans crossing a
narrow corridor at
distances up to 3 metres.
Much higher ranges are
possible if the detector is
illuminated by a remote
visible or IR light source.
Can be used at very low
light levels, and even in
total darkness with IR
LED. Full information
provided. The 1C only is
worth $16! Our price for
the assembly is:

*6 ea. or 5 for $25

METAL

CASSETTES

You can hear the
difference with these
premium quality 90 min.
pure metal cassettes.
These were recorded on
once, never played, and
then bulk erased. The
record tabs have been
removed.

s 6 ea or 10 for $50

GEL BATTERIES

Famous “high-spec”

Gates brand dual cell
batteries, enclosed in a
plastic moulding. 4V-5AHr
per pack. Connect 3
packs in series to obtain a
12V/5AHr battery. Brand
new, fresh stock, fully
charged. Limited stocks at
a giveaway price of:

*18 or 3 packs for $45

High quality military bin¬
ocular IR viewer. Self
powered, and originally
intended to be mounted
on a helmet. Focus is
adjustable from 1 metre to
infinity. Requires some IR
illumination. Powered by
one single 1.5V battery.
Original fibreglass carry
case provided.

Limited stock.

ON SPECIAL

*500

MUSIC ON HOLD
PCB

PCB assembly based on
a 7910 CF LSI music
generator 1C. Plays
Greensleeves or Home on
the Range, with a sound
quality which is hard to
believe. Full chords and
accompaniment. Also
produce two different
alarm sounds. Apply
1.5-12V across two of
connector pins to obtain
music. Copy of E.A.
project (Dec. 80)
employing this 1C is
provided.

$ 5 ea.

SOLAR PANEL
GIVEAWAY

Brand new 6 volt 1 watt
amorphous solar panels,
150m x 150mm, will
deliver one watt whilst
charging 6-8V batteries.
Two of these in series
make a great 12V battery
maintainer/charger. Have
weather protection, and
terminating clips are
provided. Incredible
pricing:

*10 ea or 10 for $85

UV PENS

The writing of these pens
is only visible under UV
“Black Light".

ea or 5 for $18

PIEZO SIREN

Stock up on this limited
stock surplus item. Brand
new, 6-12V (6V/50mA,
12V/150mA). Giveaway at:

*6 ea or 5 for $25

NICAD BATTERY
PACK

A complete nicad battery
power pack that was
intended to be used in
emergency lighting
application. Contains 17
"D" size 1.2V/4 AHr
batteries which can be
easily separated into
individual cells. New
packs in their original
packina

$ 75 per pack

ULTRASONIC

TRANSDUCERS

Scoop purchase! High
quality “Murata" 40kHz
ultrasonic transducers.

$ 4 per pair

Ring for higher quantity
pricing

LARGE LCD
DISPLAY MODULE

*620

,ND THE SPECIFICATION SHEET

Brand new large Hitachi
LM215XB display, as used
in some laptop
computers. Yellow-green
LCD reflective type, 480 X
128 dot display, effective
display area of 242 X 69
mm, has 14 LSI ICs
mounted on the rear of
the PCB. Includes four
pages of data sheets.
Limited stock at a small
fraction of their
real value. ^oy ea.
Controller kit available for
$25 including instructions.

EHT GENERATOR

Based on a brand new,
very compact modern
EHT flyback transformer
which includes an EHT
diode rectifier. We supply
the transformer, a very
simple circuit, and the
components to suit. All
you need to make a very
simple EHT or DC or
pulsed AC supply.

Powered from 12V DC
supply. Great for EHT
experiments, EHT testing,
plasma displays (large
light bulbs can be used)
etc. Total price for the
transformer and the*. - —
components is only ^ | (

BARGAIN

MONOCULAR

VIEWER

A very small but complete
IR telescope which only
needs an EHT power
supply, which is provided
in kit form. PCB and all
on board comp’s only.
Limited stock at a
reduced special price.

*229

LASER GUNSIGHT

Small black
anodised metal
body. Removable
pressure switch.

Vertical and
horizontal adjust¬
ments. Battery
life more than 10
hours

continuous. 5mW
670nM class MIA
laser. Range is about 150m, some would claim three
times more. Shock tested to 2000g. One year warranty.

ON SPECIAL AT *249

Price includes one rifle or pistol mount.

FILTER PCB
ASSEMBLY

INFRA RED
NIGHT VIEWER

These matching
components were
removed from brand new
IR tank viewers. They
include a large low light
objective lens, a large
prefocussed IR image
converter tube, a power
supply or power supply kit
to suit the tube and an
adjustable eyepiece
assembly.

Make a professional infra
red night viewer
at a ridiculous $HQQ
price of: I %/

For the set.

VISIBLE LASER
DIODE

POINTER-PEN

Suit teachers, doctors,
businessmen, and other
professionals. Improve
and enhance all your
presentations. Not a kit,
but a complete
commercial pen sized
laser pointer at an
incredible price!

ON SPECIAL AT

*180

Small pen sized body.
Runs on two small AAA
battery. Battery life: 2-10
hours. Visible 5mW red
(670nM) laser. Projects a
visible red spot at more
than 50 metres. As used
for medical treatment by
doctors and
acupuncturists.

PROJECTION LENS

Brand new large precision
projection lenses, which
were originally intended
for big screen TV
projection systems. Will
project images at close
proximity, onto walls and
screens and it has
adjustable focussing.

Main body has a diameter
of 117mm and is 107mm
long. The whole assembly
can be easily unscrewed
to obtain three very large
lenses: two plastic and
one glass. The basis of
the cheapest large
magnifier or projection
system? Experimenters
delight at

ONLY $ 28

(Item No. 0137)

Contains mainly 8 modern
ferrite transformers which
are very easy to
disassamble and rewind.
Ferrite halves are clipped
together and no
adhesives are used
between them or in coil
winding. There are four
identical small
transformers and four
indentical larger
transformers. The
transformers can be
rewound for use in
inverters,

inductors, filters, etc.

*5 ea

MINI GAS LASER
SPECIAL

Very small tube and
inverter to suit; suit long
range gunsights, laser
pointers. Incredible value

at *150

Includes tube, supply and
ballast resistor

STEPPER MOTORS

These are brand new units,

main body has a diameter of

58mm and a height of 25mm.

Will operate from 5V, has 7.5
deg. steps, coil resistance 6.6

SHsr

•4:.

ohm and it is a two phase

type. Six wires.

ONLY S 12 ea. (Item No. 0140)

• ■

Brand new, large MIL-
SPEC guages. Overall
diameter approx. 130 mm.
Pressure guage reads
from 0-16 bar.

Temperature guage reads
from -20 to 80 deg C
and has a remote sensor
attached to a 2m lead.

Pressure guage *32

Temperature $OQ
guage

MYSTERY LASER

We have accumulated a
good supply of some new
and used tubes and
heads with powers in the
range of 0.5-2mW. These
may have some small
beam geometry problems.
The tubes and the heads
are guaranteed for one
year! You can purchase
one of these tubes/heads
with our Universal 12V
laser inverter kits for the
price of the inverter only!

*79

OTHER

PRODUCTS

We have heaps of lasers
and night vision
equipment.

OATLEY ELECTRONICS

FOR SPECIALISED ELECTRONIC
ITEMS, COMPONENTS AND KITS

PO BOX 89, OATLEY, NSW 2223
Telephone: (02) 579 4985 Fax: (02) 570 7910
Certified p&p: $6 in Aust. NZ (Airmail): $10

READER INFO NO. 39

Adilam Electronics,
Setting new standards in the world
• of electronics distribution.

■■

RNE SYDNEY b

3Se - Suite 1, Ramsgate Plaza,

water 3153 191 Ramsgate Road,

4, Bayswater 3153 Sans Souci 2219

(03) 761 4466 Telephone: (02) 529 2277

(03) 761 4161 Facsimile: (02) 529 5893

(008) 800 482

READER INFO NO. 40

LEDs Plugs Rectifiers c Relays
Terminal Blocks Varistors

The Component Specialists

Capacitors ■ Connectors c Fans c Filters
Resistors c SCRs • Triacs Sockets

Headers

Switches

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